


Of Barnacles and Mermen [+Podfic and Fanart/Coloring Pages]

by xinasvoice



Series: Mer AU [1]
Category: Harry Potter - J. K. Rowling
Genre: Anal Sex, Animal Death, Artist Remus, Asexuality Spectrum, Beach Sex, Coral Reefs, Demisexual Remus Lupin, Demisexuality, Ecology, Enemies to lovers a little, Fanart, Gray-Asexuality, It’s basically HP except everyone but Remus is a mermaid and the statue of secrecy is chill, James and Sirius are both unspecified merfolk nonwhite (approximately polynesian and african), M/M, Mermaid Sex, Modern Era, Oral Sex, Outdoor Sex, Podfic, Podfic & Podficced Works, Podfic Length: 4-4.5 Hours, Strangers to Lovers, True Love, WARNINGS:, and no not with convenient legs, brief nongraphic mention of childhood neglect, chosen family, magical au, merbaby harry, mermaid au, mermaid james, mermaid sirius, poc characters, scientist remus, sirius' tail plays a significant role in this encounter, the ocean is fucking amazing
Language: English
Status: Completed
Published: 2020-12-05
Updated: 2020-12-25
Packaged: 2021-03-10 03:40:00
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 6
Words: 38,654
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27897685
Author URL: https://archiveofourown.org/users/xinasvoice/pseuds/xinasvoice
Summary: A deserted island is the perfect new home for a werewolf who is sick of chains, cells, Ministry regulations, and—to be perfectly honest—humans in general. Only, Remus hadn’t realized that, while the island itself may be deserted, the reef surrounding it is home to an unusually beautiful and territorial merman.Includes podfic and two coloring pages.
Relationships: Sirius Black/Remus Lupin
Series: Mer AU [1]
Series URL: https://archiveofourown.org/series/2073867
Comments: 110
Kudos: 229





	1. Barnacles

**Author's Note:**

  * For [TheHufflebean (SevralShips)](https://archiveofourown.org/users/SevralShips/gifts).



> If I may make a recommendation, you could listen to the podfic while coloring (see Chapter 6 for the coloring pages) if you are looking for a truly immersive coral reef experience. Have fun!
> 
> Podfic duration: 4hr 16min  
> [.m4a audio file](https://soundcloud.com/user-824292289/of-barnacles-and-mermen) ~ [.m4b audiobook file](https://drive.google.com/file/d/1K0g66289ihfspng7T_ft2gLy6B0fdvky/view?usp=sharing)
> 
> Ending music is [Aerial Promenade](https://soundcloud.com/fasithea/aerial-promenade-seagull-orchestra) by Seagull Orchestra
> 
> Thank you to beta reader [ForeverShippingJohnlock](https://archiveofourown.org/users/ForeverShippingJohnlock/works), who read this story in less than 24 hours even though I made her cry. 
> 
> Gifted to TheHuffleBean because once I had the idea for this story, I went cruising to see what other wolfstar mermaid aus are out there and their story, [Siren Songs](https://archiveofourown.org/works/23039380), made me weep with how good it is.

[ ](https://www.flickr.com/photos/158228914@N03/50756313908/in/dateposted-public/)

[xinasvoice](https://soundcloud.com/user-824292289) · [Of Barnacles and Mermen](https://soundcloud.com/user-824292289/of-barnacles-and-mermen)

It was a very small island, no more than a mile across, and about half as wide. Long ago, it must have been volcanic in nature, and the majority of it was still coarse, black rock, with the exception of a little valley just large enough to support an overgrown orchard. The lighthouse at the east end was similarly run-down, and the only other attraction anyone could have called such was the narrow, black-sand beach on the south shore. It was only a few meters wide and surrounded by tide pools, but the lagoon and semicircular reef beyond were huge and truly lovely. The climate was agreeable, nearly tropical and without harsh winters to survive through, only a mild monsoon season in the late summer.

That was all very well, but the only thing that truly mattered about the island was that it was very far from everything and everyone else. It was, therefore, the perfect new home for a werewolf who was sick of chains, cells, Ministry regulations, and—to be perfectly honest—humans in general.

Due to the werewolf issue, Remus Lupin was nowhere near wealthy enough to buy his own private island—he probably couldn’t have afforded a bucketful of the lustrous, black sand—but he knew someone who knew someone who knew the shipping company that had long ago given up on the lighthouse, and he had managed to convince them that his magical creatures degree could be put to use there. The magical community was woefully ignorant of marine species, he argued, and the amount of knowledge (and profit) that could be gained was significant. It hadn’t taken much to convince them, even though the only magical creature he knew for a fact lived there was an unassuming and surely extremely boring (and unprofitable) species of barnacle. He hadn’t asked for much, just a portkey and enough supplies to keep him alive. That, and an ironclad guarantee that he wouldn’t receive any unexpected visitors, especially on the full moon.

That hadn’t been hard to arrange either. He suspected the shipping company thought relocating his dangerous werewolf self was an act of community service, and it was probably that, more than any uninspiring promises of barnacle discoveries, that had gotten him the position.

And now, here he was. The moment his feet landed in the sparse grass outside the dilapidated lighthouse, he breathed a sigh of relief. He was hundreds of miles from any other human habitation—and thousands of miles from the nearest mainland—which meant he was hundreds of miles from anyone who would care that he turned into a monster once a month. Hundreds of miles from all of his exes, too, and from the temptation to try any kind of intimate relationship ever again. Casual sex had never appealed to him, and the few serious relationships he had tried on for size had each been their own separate disaster—again, thanks to the werewolf issue.

All that was over now, and while another man might have felt loneliness or despair at the thought of such a solitary existence, when Remus walked to the cliff and looked down at the pristine, blue-green lagoon, utterly devoid of all sentient life, he felt only peace. The sun was brighter than it ever dared to be in foggy, smoggy London, and its heat was soothed by a soft, cool breeze that ruffled through his curls, caressing him far more pleasingly than any lover could. He would much rather have this island—and a practical relationship with his own right hand—than the entire queer scene back home.

He turned to look at the lighthouse, which did indeed look run-down, but it was nothing a few charms couldn’t fix. He only had to make it comfortable for himself, after all. The shipping company had stopped formal operation of the signal light at the top when the shipping lanes had moved several hundred miles to the north.

Not even ships would come here, Remus reminded himself with satisfaction. He really was alone. He took a deep breath of the salty, loamy air. Yes, this was a good place.

He dropped the last of his bags on the lighthouse stoop—feeling a thrill at the thought that no one would disturb them or steal them, because there was _no one here_ —and set off to explore his new territory. The trees in the orchard were overgrown but heavy with fruit, an unexpected boon. There was also a flat patch of land that he assumed had been used as a vegetable garden before. The lighthouse company had given him over a year’s worth of canned and magically preserved food, but he was looking forward to the challenge of providing as much of his own food as possible. It shouldn’t be too difficult to garden, considering the rich, volcanic soil, plentiful sun and rain, and the books full of do-it-yourself garden charms in his bags. That and fish from the ocean should give him a much better diet than the boxed cereal and dried noodles that he had existed on in London.

The path down to the beach was also unkempt, and he took his time, trimming back the undergrowth with his wand as he went. He would likely walk this way at least once a day, and he already found himself motivated to make the whole island look its best, to care for it as he hadn’t ever done for his dreary basement flat.

Even with the impromptu landscape work, it took barely half an hour to reach the smooth, black sand. He smiled and kicked off his shoes and socks, letting his feet sink in, and then turned his head to squint down the beach when something oddly bright caught his eye. It was a reflection of light, like off a pane of glass, from something in the rocks down at the other end of the beach, where the sand met the rocky tide pools that surrounded the rest of the island. Remus stared at it, but for the life of him he couldn’t make out what it was until he walked down the beach to the water and the change in perspective made it suddenly clear what he was looking at.

The bright morning sunlight was reflecting off scales on a long, black and silver tail, which belonged to a mermaid, who was lounging on a smooth, black rock, their tail half in the water and floating lazily up and down with the lagoon’s gentle waves.

Remus’ first reaction was annoyance. He was supposed to be alone here, and merfolk, while not human, were type A fully sentient creatures, and therefore definitely counted as people. He sighed. At least this person wouldn’t likely come knocking on his door and pestering him. Perhaps they were only here for the day, regardless. Perhaps Remus could _convince_ them to be here only for the day.

He walked down the beach, through the wet sand right at the edge of the water. As he got closer, he shifted his assessment from mermaid to mer _man_ , as the lean, flat-chested figure sprawled on the rock was definitely not female. He also appeared to be fully asleep, and, it had to be said, fully gorgeous.

Despite his magical creatures degree, Remus didn’t know that much about merfolk, or marine life in general, a fact which he had carefully obscured from the shipping company. He did, however, know that the human-looking parts of merfolk were usually quite attractive, to help with the whole ensnaring-sailors gig that they had originally evolved for, but this one had to be something special, even among his own kind. His skin was a luscious light brown and decorated with tattoos, which Remus had had no idea were even practiced among the species. There were inky rings around his biceps, patterns of circles and dots that almost looked like star constellations on his shoulders and chest, and jagged lines like lightning that highlighted his narrow hips and navel. His long hair was the same midnight black as his tattoos, and it spread out around his head on the rock in a ludicrously perfect swirl, framing his well-sculpted face like he was an art nouveau print. His face was turned slightly away, which only served to highlight the lovely curve of his neck and collarbones.

From the hips up, he seemed almost entirely human, the only exception being the complete lack of chest or underarm hair and the webbing between his fingers, which was darker than the rest of his skin. His hands were beautiful too, with long, elegant fingers and narrow wrists.

Of course, below the hips he was completely unlike a human. His tail was much longer than Remus would have supposed, more than twice the length of the rest of his body. It was about the same width as his hips for several feet before tapering down to meet the large fluke. There were several smaller fins along the sides and back as well, which Remus could only see vaguely under the water.

The merman’s skin transitioned to scales in a gradual way around his lower hips, and they were mostly black except for a line of exquisitely shaded silver along the exposed underside. This led the eye down to the large fluke at the bottom, which was nearly as wide as Remus’ spread arms. The fin looked both strong and delicate, with thick webbing at the base that gradually thinned to a silver, almost lacy frill at the end. It floated elegantly on the surface of the water, the translucent fringe of it blending seamlessly with the seafoam.

He was lying with his arms laid out above his head, perfectly relaxed, and clearly entirely asleep and unaware of Remus’ presence. His hair was nearly dry, so Remus could only assume he had been sleeping there in the sun for a while.

Remus stood there for a moment more, thinking it was best if he finished gawking before he was noticed, but when the merman simply kept sleeping, he realized he would have to do something. He shuffled his feet in the water a little, and, when that provoked no response, cleared his throat.

The merman’s eyes fluttered open, but he was still turned away, and Remus caught only the barest hint of silver before they drifted closed again, perhaps deciding that whatever small sound he had heard was nothing worth interrupting a nap for. Remus pursed his lips and took a more direct approach.

“Hello.”

He spoke in his most friendly voice, but the merman still startled violently, his entire body jerking. His tail convulsed at the same time, throwing up a huge spray and somehow managing to propel him into the air several feet, as, in a clearly instinctual reaction, the creature threw himself back into the water in a single, graceful arc. It was such a dramatic reaction that Remus took several steps back, wiping water from his face.

The merman resurfaced a moment later, black hair now slicked and arranged around his face like parted curtains.

“What-who-who the _fuck_ are you?“ he demanded, propelling himself quickly back through the shallow waves to rise up in front of Remus on the wet sand, his beautiful face pulled into a scowl.

He was managing to balance on the lower half of his tail in such a way that he was actually a good two heads taller than Remus, rather like a cobra in an aggressive posture. Remus was so taken aback by being loomed over by the most aesthetically appealing person he had ever seen that he was momentarily speechless.

“What are you doing here, human?!” the merman asked, crossing his arms, and Remus startled a bit at the splashing sound that accompanied the question, as the end of the merman’s tail slapped the shallow water impatiently.

“Sorry!” Remus gasped at last, his hand going to his wand in his pocket, although he refrained from drawing it. He stepped back a few feet onto the dry sand, trying to give himself enough space to think about something other than the shape of the creature’s folded arms, or the way the water streamed from his hair and down his chest in trailing patterns. “I’m Remus Lupin. I didn’t mean to startle you.”

The merman narrowed his eyes. “And what are you doing here, Remus Lupin, the human? Or should I say, the _wizard_ human? I see that wand sticking out of your pocket. Don’t even think about using it. I can do magic too, and you wouldn’t like it.”

Remus snatched his hand away from his pocket and straightened his shoulders. He had no idea what kind of magic merfolk could do, and while he was curious, he didn’t want to find out like this. “I—well, I live here now. I was sent by the Southern Star Shipping Company to study the _Balanus nubilus_ that live here.”

“There's none of those here,” the merman said, hardly waiting for him to finish.

“They're a type of barnacle—” Remus started to explain, but the merman‘s perfectly symmetrical black eyebrows just drew together even further.

“I _know_ ,” he snapped and gestured with his fingers rather close to Remus’ face. “ _Balanus nubilus_ , crustaceans of the class Cirripedia, about this big with blueish-gray shells, and they were an invasive species, so I got rid of them and allowed the _Balanus crenatus_ to recolonize their areas since those, unlike the _Balanus nubilus_ , are actually a food source for the ochre stars.”

“Oh,” Remus said, feeling himself deflate a little at hearing this, and also a little thrown off that the merman not only knew what _Balanus nubilus_ were, but also seemed to know something about how they fit into the local ecosystem. Remus hadn’t known a barnacle from a sea sponge before a couple weeks ago. He hadn’t realized they were an invasive species. All he knew was that there were drawings of them in the journal the notes the lighthouse keeper had sent to the shipping company, and that they secreted a sticky substance that might be of use in potions.

“It seems like there is not, in fact, a reason for you to be here,” the merman said smugly. “So you can go now.”

“I’ll study the _Balanus crenatus_ , then,” Remus said, rallying. “The Southern Star Shipping Company is just as interested in those, and they’re paying me to live here, so I have to do my job.” Remus was fairly sure the Southern Star Shipping Company didn’t know a barnacle from a beetle, and wouldn’t give a fuck even if they did _._

“Absolutely not,” the merman said, his voice firm. “You can’t live here. This is _my_ island, and you, yourself are a destructive, invasive species.” He reached down to point his finger at the center of Remus’ chest, nearly poking him with it.

Remus wavered for a moment at that but dug in his heels. He had done _months_ of research to find this opportunity. He was not going back to cold, dreary London after hardly spending an hour here, not for anything.

“Actually, the shipping company owns this island. I have every right to be here.” He drew himself up as tall as he could, forcing himself not to flinch when the merman levered himself up another few inches as well.

“This area was reclaimed by the Southeastern Democratic of Mer in the treaty of 1987,” the merman countered, but Remus was ready for this one. The shipping company had told him that much, even if they hadn’t mentioned that this particular island was being claimed by an unusually beautiful and territorial merman. The treaty was, in fact, the entire reason the shipping lanes had been moved.

“I believe that treaty only applies to the water surrounding the island, not the land itself.”

The merman’s lips twisted in frustration. Clearly, he had known as much and had hoped Remus would be ignorant of it. “Only because the council didn’t yet fully understand the impact of land-dwelling colonizers like yourself on the local marine systems—“

“I’m just one person, I’m not going to upset the local marine system!” Remus protested. When the merman looked ready to argue with him again, he decided to switch tactics, coaching his voice and posture away from challenge and into calm. If merfolk were indeed territorial, he should be projecting respect and submissiveness, not arguing. “Look, we are clearly getting off on the wrong foot here.” He paused as the merman lifted one unamused eyebrow at the idiom, but soldiered on. “I should have started by apologizing. They didn’t tell me a merman was living here or I would have reached out before arriving.”

He was vaguely aware that the various democratics of Mer had methods of regular communications with the outside world—not owl post, obviously, but _something_ —so that wasn’t such a stretch. He would certainly have made an effort.

The merman did not seem mollified. He rolled his eyes—which Remus could now see were indeed the same silvery gray as the underside of his tail.

“Mer _man_ ,” he repeated with disdain. “You humans are always making assumptions. How do you know I’m not a mer _maid_ , hmm?”

“Sorry!” Remus blushed, now truly embarrassed for the first time. He was well aware that merfolk were sexually dimorphic, just like humans, but, again, just like with humans, that didn’t mean that gender was as obvious or as binary as one might think. “I shouldn’t have assumed that. It was very rude of me. Please, would you tell me your name and how I should address you?”

The merman’s fluke twitched restlessly in the shallow waves, and he sighed, reluctantly lowering himself down a few inches. “It just so happens that you were right about my gender. And my name is Sirius. Like the southern star that bloated company was probably trying to name themselves after.”

Remus glanced down at the tattoos on the merman’s chest that he had thought looked like constellations before and easily found three near his lowest ribs that were lined up in a precise row. He followed the line they created to the largest tattooed dot, which was placed in the precise center of his chest, over his sternum, in exactly the same orientation as it appeared in the summer sky.

“Thank you, Sirius. I really am sorry for startling you, and for showing up unannounced. But, surely, we can make this work. You can hardly need the land part of this island yourself. The lighthouse is clearly unused, and the rest of the island seems to be entirely uninhabited and uncared for.”

The merman—Sirius—scoffed. “Of course it’s unused, it’s _land_. But that doesn’t mean I want you living there. And I do use the beach. That is _my_ rock.”

He pointed at the place where he had been sunning himself, and Remus realized belatedly that it was smooth and exactly the right size for a merperson to sun himself on not by coincidence, but by design. It looked like it had started out a natural formation, but it had clearly been polished and shaped to make it more comfortable.

“I would be happy to leave you to use it in peace,” Remus said with complete honesty. “I came here looking for solitude. I won’t bother you. I don’t even need to go in the water to study the _Balanus crenatus_ , just around the tide pools.”

“Having a bunch of humans traipsing around my tide pools is exactly the opposite of leaving me in peace,” Sirius said sharply, clearly not swayed.

“I’m not a bunch of humans,” Remus repeated patiently. “I’m just me.”

“And how long until the rest of your pod arrives?” Sirius demanded. When Remus looked bewildered, he sighed with exasperation and clarified, “School, flock, group, whatever you call it. Family, friends, other humans obsessed with crustaceans who are just trying to mind their own business!”

“Oh. I haven’t got anyone like that. I told you, I’m alone.”

Sirius’ eyes widened, and he lowered himself down more so he was almost at Remus’ eye level, his expression softening. Remus’ insides twisted with irritation. He had gotten over feeling sorry for himself, and he didn’t like the idea of this excessively perfect merman pitying him. But, if that was what it took…

“I don’t have any family or friends. No one else is coming, and you won’t even notice I’m here.”

Sirius pursed his lips, clearly wavering at last, and Remus waited, head bowed respectfully.

Finally the merman relented. “Fine. But you’re not to disturb the barnacles or anything else here while you do your research. Observational, non-invasive methods only. No dumping your nuclear waste in the water either.”

Remus suppressed a snort. “I haven’t got any nuclear waste.”

“I’m just counting all the jellyfish,” Sirius said, looking down his nose at him again. “No dumping your organic byproducts either, no fecal matter, not even hair clippings. I’ll know if you do. Do you know what electroreception is?”

Remus racked his brain for a moment, and managed, “Sensing electrical currents through the water?”

“Yes, like those in your awkwardly swimming body, and I can sense movement in the water too. So, if you put one knobbly, clumsily evolved _toe_ into my lagoon, I’ll know it.”

Remus had heard of sharks having senses like that, and it made sense that merfolk would too, but he was a bit skeptical about it being as precise as Sirius was claiming. After all, Remus had been wading in the water a few moments ago and he had managed to sneak up on Sirius without even trying.

“Does that mean fishing is out of the question?” Remus didn’t love the idea of subsisting on the canned meat he had brought with him, but he would if he had to, or convert to vegetarianism. It wasn’t like he could keep livestock. The island was too small for anything but chickens, and those would probably end up “disrupting the local marine system” with their “organic byproducts.”

Sirius considered this. “You may fish, but only with my guidance. You’re not to start randomly throwing hooks into the water, and you can’t use your wand either. It’s an unfair advantage.” 

Remus nodded, although he had no idea how to fish without either a rod or his wand. Did Sirius expect him to somehow catch fish with a spear or handheld net… _without_ going in the water? But it didn’t matter. As long as he could stay, he would put up with it. He didn’t fancy fishing under the surly eye of an overprotective merman anyways. The idea made the canned tuna in the crates he had brought seem very appealing.

“That won’t be a problem. Thank you.”

“If you do cause problems, there will be consequences,” Sirius said, looming up a bit again. “My brother is on the council. We’re talking an _international incident_. Understand?”

“I understand.”

“Good.”

Silence reigned for an awkward moment. Remus wondered how Sirius would be reacting right now if he had known Remus planned to transform here once a month. As a merman, Sirius would be safe from the wolf, but Remus couldn’t guarantee the wolf wouldn’t try to go in the water. As far as international incidents went, that seemed like a problematic one, but Remus decided to take this one issue at a time and said nothing. He had a whole month. It would be better to wait until he had built a little trust with Sirius before telling him he’d brought an actual monster along with his human self.

While mulling this over, Remus found himself watching the way Sirius’ tail twitched, stirring up the black sand under the waves. From this perspective, he could see the delicate, frilled fins on the back side better. Like the fluke, they shaded elegantly from night-black to translucent silver at the tips.

The tail lifted as Sirius wrapped it around himself, rather like a cat, the wide fluke relaxing onto the wet sand. Remus glanced up and found Sirius watching him, his expression unimpressed.

“I-I’ll just go settle in, then.” Remus made a strategic retreat, scooping up his shoes along the way, and went to start unpacking.


	2. Coral

He stayed away from the beach for as long as he could after that, using fixing up the lighthouse as an excuse. It wasn’t entirely made-up. There was a lot of work to be done to make it first habitable and then comfortable. Then there was the garden to set up, and the orchard to prune. Magic made awkwardly quick work of all of it, however, and after the third day, Remus was so much at loose ends that he couldn’t excuse putting off starting his research any longer. He was supposed to send weekly updates to the shipping company, which he was sure would be diligently filed without ever being read.

The lighthouse was on the tallest part of the island, but not so high up that he couldn’t see the beach and the lagoon clearly every time he looked out his window. Sirius was indeed on the beach every day at low tide, lying on his rock with an air of stubborn determination, even when a brief rainstorm rolled in and the sunning advantages were dubious. At high tide the rock was submerged, and then Sirius could usually be seen in the clear water of the lagoon, swimming to and fro beneath the surface and doing Remus had no idea what. Hunting, perhaps, but surely even a creature as large as Sirius didn’t need to hunt for half a day in these rich waters.

When Remus finally ventured down to the shore, he went first to the north side of the island, on the opposite side of the beach, trying to show he wouldn’t be a nuisance. There were a few tide pools there, but it was far less pleasant than the lagoon, as there was no substantial coral reef to temper the waves, and the slope was steep and rocky. He charmed his notes to be waterproof and did what he could while getting blasted with sea spray every few seconds. He was also well aware that he was being watched. He could see Sirius’ long, dark body prowling around beneath the waves, even though it was low tide and Sirius would probably normally be sunning himself.

By the end of the morning, Remus was grumpy and fed up. If Sirius was going to follow him around regardless, he might as well go where it was comfortable.

He saw Sirius’ dark-haired head bob up as he turned to walk up the slope, but neither of them acknowledged each other. Sure enough, by the time Remus had made the short walk to the other side of the island, Sirius had already come all the way around and was lying out on his rock in an artful pose that was probably meant to suggest he had been there the whole time. He didn’t even look winded, and it made Remus wonder how fast he could swim when he wanted to.

Remus started at the other end of the beach, to make a show of not disturbing Sirius any more than necessary. Sirius, for his part, made a show of being disturbed. He propped himself up on his hands and watched Remus through narrowed eyes, probably keeping watch to make sure Remus didn’t suddenly throw a barrel of nuclear waste or fingernail trimmings into the water.

Remus did his best to ignore him and focused on his work, making tidy drawings of the barnacles, noting their arrangement, average measurements, and density in each pool. It wasn’t what anyone could call inherently interesting work, but it was what he had. Maybe something interesting would come of it, eventually.

After a while, he saw Sirius slide into the water out of the corner of his eye. He wasn’t sure if the merman thought he was being stealthy or not, but Remus could see him clearly as he swam with theoretical casualness around the lagoon, making slow circuits that brought him a bit closer each time until finally he surfaced nearly at Remus’ feet, in a deep part of the water right next to where the rocky tide pool ended.

“It’s been three days,” Sirius said bluntly, his mouth barely above the water. “Are you not going to fish?”

Remus shrugged, continuing with his drawing. “Your regulations made it rather difficult. And I don’t really need to.”

Sirius drifted a bit closer and hummed with curiosity. “Humans need protein, don’t they?”

“I have canned fish in my supplies. There’s no need to concern yourself.”

“Canned?” Sirius recoiled, obviously horrified. “That sounds vile!”

“It’s not as bad as you might think,” Remus said, still focusing on his journal and refusing to look at him. Sirius had styled his hair into two long braids today, and they were floating languidly in the water behind him. “Or, at least, I don’t mind it. You might indeed find it vile, O Prince of the Sea.”

Sirius scowled. “The Mer are a _democracy_ , Remus the human, and have been since long before your species gave up hanging each other for fun.”

He dove away with a little flounce of his tail that sent a significant spray of water in Remus’ direction, probably on purpose. Remus, who had been getting a bit overheated as the day wore on, decided to take it as a favor.

A few minutes later, Sirius reappeared and tossed two orange and gray fish onto the black sand next to Remus’ current tide pool. “There. Eat those. They’re overpopulated, and I can’t eat them all myself.”

Remus examined the fish, which he was relatively sure were one of the non-toxic species he had made a list of before arriving. Each one had been dispatched with a tidy stab wound at the base of their skull, severing the spinal column. It was very precise work.

“Do you use a spear?” Remus asked. He had yet to see the merman with any sort of tool, and he definitely didn’t have one on him now.

Sirius smirked and pushed himself up halfway onto the beach. His tail lashed out to one side, slamming down into the sand so close to Remus that he felt it brush his arm. When Sirius lifted his tail away a moment later, the sand held an imprint in the shape of his fluke, which had been clenched into a narrow triangle, not at all the usual, luxurious shape. There was also a puncture mark that looked to be about eight inches deep, identical to the ones in the fish.

Remus looked back at Sirius’ tail, which he had laid out on the sand in proud display. Sure enough, there was a corresponding spike of bony cartilage right near the base on the dorsal side. It was solid black and blended well with the more delicate fins around it, or Remus might have noticed it before. As Remus watched, it and the fins around it stood up in display and then slicked back down, clearly under Sirius’ conscious control.

“You really don’t know much about us, do you?” Sirius asked with his brows lifted. “For a researcher, you seem awfully ignorant of marine life.”

“I’m here to study barnacles, not merfolk,” Remus said, refusing to rise to the bait.

“Too bad,” Sirius said with a scornful air. “They’re probably the most boring things in this lagoon.”

With that and one powerful heave of his tail, he flipped himself backwards into the surf.

+++

Over the next week, there were several more little interactions like this. Sirius would bring Remus a fish or two, or ask to see Remus’ notes. He enjoyed making corrections to these whenever possible, and Remus had to admit the merman had an impressive body of knowledge about sea life, even the supposedly boring barnacles. It made Remus feel a little superfluous, to be making basic notes about the shape of a shell when Sirius would then swim up and rattle off facts so quickly that Remus couldn’t even write them all down. If the Southern Star Shipping Company had actually cared about investigating barnacles or anything else, they would have done better to simply interview one of the Mer, rather than send Remus.

Several days later, Sirius swam over to examine Remus’ notebook and flipped through it with an impatient, restless air and then tossed it aside.

“Go in the water. They have a triphasic life cycle. You’ll never understand the larval phases if you just sit up here in the air.”

Remus raised his eyebrows. “I thought going in the water would cause an international incident.”

“I’m changing my mind. Temporarily,” Sirius said primly, flipping his wet hair, which was loose today, over his shoulder.

“Also, aren’t barnacle larval stages microscopic?”

Sirius sighed in the manner of one who had already endured a lot. There was a very subtle tinge of pink on his brown cheeks, which as far as Remus could tell, did not grow facial hair. “Stop being a bottom feeder and let me show you my reef already.”

He propelled himself back into the water in that dramatic way of his, and Remus hid a smile. He had wondered how long it would take for Sirius to cave on this issue. He clearly loved everything about the lagoon, and it must be lonely for him here, having no one to share it with. Unlike Remus, most people weren’t excited to spend their lives alone, and Sirius did seem to be on his own here. It had been more than a week, and Remus hadn’t seen any sign of other Mer.

Sirius popped up beyond the waves and swam back over to Remus, although he kept himself in the water. “You’re not going to drown are you?”

He asked this in the wary, untrusting manner of one handing a toddler a knife, as if a disastrous outcome was only a matter of time.

“I can swim,” Remus assured him. “And I’ll use a water-breathing charm. I won’t drown.”

“Or bleed?” Sirius pressed. “You shouldn’t bleed here. There are sharks. They prefer to hunt at night, but they‘ll swarm if they smell blood, no matter what time it is.”

“I have no intention of bleeding.” Remus waded into the cool water, excited to finally be able to see the reef he had been looking at through the waves for days now. Also, it was _hot_. Working in the heat next to the taunting relief of the water was torture. Quickly, he cast the water-breathing charm and underwater vision charm he had practiced before arriving at the island and set his wand aside above the tide line.

“Stop.” Sirius surged forward, swinging his tail around in the manner of one putting out their hand, incidentally splashing Remus full in the face. “What are you doing?”

Remus wiped his face, trying not to splutter, and glared down at Sirius, who was still low in the water. “Swimming?”

“In _clothing?_ ” Sirius looked at him as if he were not only a toddler, but a daft one.

Remus glanced down at his thin linen shirt and trousers and shrugged. He honestly didn’t think it made much difference, but he could see from Sirius' disturbed expression and stubbornly folded arms that it would be easier to relent.

Undressing in front of a perfectly sculpted merman who judged him an inferior being at every opportunity was nerve-wracking, but Remus did it anyways, trying to maintain a neutral expression as he felt Sirius' eyes travel over the scars on his chest and legs. The wolf had left its mark on him numerous times. Remus was mostly used to the scars himself, but he always hated seeing other people’s reactions to them.

The water-vision charm made the world of air blurry, but as far as Remus could see, Sirius' expression seemed to be much the same as before. There was no pity there, thankfully, but he was scowling at Remus' briefs, which he had not—and did not intend to—remove.

Sirius looked down at the offending article of clothing and then back up at Remus' face, eyebrows raised. When Remus shook his head, Sirius' eyes rolled to the sky.

“ _Humans_ ,” he muttered. “All right, then, get in here.”

He didn’t wait for compliance but surged forward, snatching Remus' hand and dragging him past the shallows and under the surface in one smooth dive.

Remus was a good swimmer, but it had been a while. It took him a moment to orient himself and remember that he could open his eyes. The charm was working well. He could see the black sand below him clearly, as well as Sirius circling him, watching with an analytic eye as Remus began to swim in the direction of the coral a few meters away.

He only made it a few strokes before Sirius snatched his hand up again. Remus tugged, but Sirius didn’t let go, so Remus rose up to the surface to protest.

“You can let go,” he said, trying to be polite even as a wave slapped him in the face. “I told you, I can swim.”

“No, you can’t,” Sirius said flatly. “That is not swimming. That is _flailing_ , and, like I said, there are sharks here. You might as well wave a sign saying how delicious you and your ridiculous land-lumbering legs are.”

Remus mashed his lips together in frustration, but it was hard to argue about swimming skills with someone who could quite literally swim circles around him.

“This will be faster,” Sirius added. “Now, it’s time for the reef rules.”

Remus sighed. Of course there were more rules. “I promise not to piss in the lagoon.”

“Good,” Sirius said in an unamused voice that implied this had actually been one of the rules he was going to make. “Even more importantly, you're not to touch anything unless I do first. No poking anemones like an ignorant guppy. And you are _especially_ not to touch the coral. It's very delicate. It’s also sharp, and we already discussed the consequences of bleeding, which are...?”

He trailed off in a patronizing way, indicating that Remus should finish his sentence, like a schoolchild learning lines. Remus gritted his teeth but forced himself to say, “Getting torn apart by sharks.”

“Correct. Which would really stir everyone up, and you would not enjoy. All right. Ready?”

“Yes!”

His whole body jerked as Sirius pulled him under. It took only a second, a few beats of the powerful tail, and then they were in the center of the lagoon, floating midwater right above the reef, and Remus, if he had been breathing in a regular manner, would have gasped.

The reef was _lovely_. Remus had seen video footage of coral reefs before, but this didn’t even compare. There were more shapes and colors than any video footage could ever accurately convey. Against the dramatic backdrop of black sand was a riot of pink, red, blue, purple, and yellow coral, in shapes ranging from tiny pocketed spheres to gigantic lacy shapes larger than the length of his body and as delicate as an old-fashioned lady‘s fan. Each one was entirely unique, and Remus could easily have spent an hour drawing just one of them. There was seaweed too, interspersed throughout the coral in a whimsy of shapes, some low and craggy, some long and thin, in colors ranging from green to violet and on to fiery orange.

Overlaid on it all, were the fish. Remus had seen them glinting below the surface from his perch on the edge of the tide pools, and he had examined some of them up close when Sirius offered them for dinner, but now that he was in the water, the place seemed thick with them. Many separate schools of them were visible at any given moment, swimming in lightning-fast patterns in and out of the coral. There were also little, solitary ones peeking out from their hiding places, and slow, lumbering giants gliding smoothly through them all. The fish were even more colorful than their backdrop of coral, most of them two or three colors, shaded and striped in every combination imaginable.

It was all far more than Remus could ever hope to take in, more creatures than he could count, let alone study in any kind of detail, in an entire lifetime. And yet, all of these wonders were nothing compared to what he saw when he finally tore his eyes away from the circus of life and looked back at Sirius.

Sirius was, quite literally, in his element, and he seemed almost a different person. Sirius above the surface had looked unfairly beautiful, but looking at him now made the person Remus had almost gotten accustomed to looking at these past few days seem like a half-drowned cat. Here in the water, his hair fanned out around him, rippling and parting with his every movement, not unlike the schools of fish. His warm brown skin and dark scales glowed in the uneven shine of sunlight through the water, and his eyes seemed to be the same color as the shimmering underside of the surface that rippled above them. He moved easily, with only minute movements of the little fins on his tail needed to turn him around, so it almost seemed as if the water itself was moving him, obeying his intentions. His tail was unspeakably lovely in the water, where the light could shine through the translucent ends of his fins and glimmer iridescently off his scales. In the neutral buoyancy of the water, the smaller fins along the dorsal side and the frills at the end of the huge fluke fluttered freely, while on land they had often lain crumpled like a wet handkerchief. The difference was astonishing.

It wasn’t just appearances either. Sirius _was_ a different person in the water. His tense attitude melted away almost immediately, even with Remus along. His eyes seemed to light up with joy and satisfaction as soon as he looked at the reef in all its complexity. It couldn’t be more obvious that he adored the reef and every creature in it.

The feeling seemed to be mutual too. No sooner had they approached the reef than a school of tiny, blue fish with yellow-tipped fins rushed over and swirled themselves around him in a joyful tornado from tail to streaming black hair, as if greeting him. He beamed at them, looking up at Remus to share the moment. Remus’ chest tightened at the delight in Sirius’ smile, a thing easily as beautiful as anything else around them. He didn’t consider himself much of an artist—although his work did require him to draw the natural world—but seeing Sirius this way made him itch for his watercolors.

For all his complaining that Remus was too slow, Sirius didn’t seem to be in a rush. Their tour of the reef was gentle and meandering, and many other schools of fish came over to swirl around Sirius’ tail or hide in his hair, peeking out at Remus with flat eyes that didn’t seem to hold much intelligence, but they certainly recognized their resident merman. Even the larger fish, most of which seemed to move in lazy slow motion, tended to tilt towards Sirius when they got a chance, slipping into his current for a moment before lumbering away.

The reef was also unexpectedly noisy. The waves were not excessive here, but they did still move the sand around, creating an odd backdrop of sound, somewhere between white noise and the crunching of footsteps on a dry beach. There was also a periodic, louder clicking, a fast-paced zipping of sound. It seemed oddly familiar, but Remus still couldn’t place it until he saw Sirius cock his head down towards one of the huge gray wrasse, mouth spread wide in a grin, and Remus realized the sound was coming from the merman himself. His mouth wasn’t moving, but somehow he was making this trilling noise that Remus suddenly recognized from a long-ago seen documentary about dolphins.

He wondered if this was where the legends of mermaid song came from. It certainly didn’t seem very musical. The clicking sound of it—and Sirius’ body language—made it seem more like speech, as if he was asking the wrasse about its day here in the reef.

The fish didn’t respond in a way Remus could understand, but Sirius shook his head fondly as it moved sedately away, in the way someone might at an old friend, even though the fish surely wasn’t intelligent enough to actually be one.

The seafloor below them was almost entirely encrusted with coral, but there were a few patches of black sand as well. Sirius eagerly tugged Remus down towards one of these. Remus had by now accepted his status as a helpless passenger and went along willingly, even when his ears started to ache under the pressure. Sirius’ hand was gentle on his own, the temperature of it just a bit warmer than the balmy sea around them.

Sirius hovered over the sand with his tail pointed straight up, comfortably inverted, and tugged Remus into a similar position, and then began clicking and trilling at a dark shadow where the coral overhung the sand, expression cajoling. Remus was reminded of someone calling for their wayward pet, and, sure enough, after only a little of this, a blunt-faced eel with a gaping mouth full of teeth cautiously poked out its head, peering at them myopically.

Sirius smiled at it winningly and continued clicking as he reached out to run a gentle finger over its head. He held Remus back a bit, as if warning him not to try this himself, but there was no need. Remus had no intention of putting his fingers anywhere near that mouth full of jagged teeth, no matter how tame it looked under Sirius’ elegant, webbed fingers.

Suddenly the sound of Sirius’ trilling broke off, as something in the coral above the eel caught his eye. It was a patch of pale, bleached coral, so small that Remus would never have noticed it if he hadn’t been following Sirius’ gaze. Sirius’ face grew sharp with concern and he let go of Remus’ hand to cup both of his own around the white branch of coral, cradling it through the water without actually touching it. He closed his eyes for a moment, as if concentrating, and then made a different noise, less clicking and more like a hum. The song—for this was clearly actually a song, unlike the dolphin trills—drifted up and down in almost clumsy waves, clearly challenging for Sirius to produce. As Remus watched, the coral slowly began to respond. It seemed to fill out, the white, bony protrusion growing softer and pinker, closer to the dark red color of the neighboring branches.

Sirius’ worried expression gradually eased as the coral recovered at his urging, which had to be magical in nature. Finally, he withdrew his hands with another trill of marine speech. He glanced over at Remus, who was watching with interest. Sirius looked at him for a moment, face unreadable, and Remus lamented the fact that they couldn’t communicate effectively underwater. Instead, he found Sirius’ hand and squeezed it, smiling, trying to convey without words how impressed he was.

Sirius’ eyes widened, and then he looked away, gaze falling back on the eel, which had been watching as well, its flat eyes fixed on the merman with an expression that Remus could anthropomorphize into hero-worship. Sirius smiled at it and gave it another rub. The eel, for its part, seemed to tolerate or perhaps even enjoy this attention. It was hard to tell by looking at its face, but it didn’t retreat into its den until Sirius finally turned and let himself drift back upright, being careful not to disturb the eel or the surrounding coral with his fluke.

Sirius gradually led Remus deeper and deeper as the seafloor began to fall, and eventually they came to the darker blue water where the reef disappeared, as they approached the drop-off. Remus stared into the deep azure of it. The ocean here was seemingly bottomless, and the view was as close to endless as made any difference on this planet. Sirius paused as well, and they spent a moment looking out at the emptiness together.

Suddenly Remus’ attention was drawn by movement towards his left, and he pulled hard on Sirius’ hand, recoiling at the sight of a group of five or six sharks drifting towards them. They were on the small side compared to the behemoths that frequented the open ocean, only a little over a meter long, but their gaping mouths held an inherent threat.

Sirius was clearly unfazed, but he did calmly swim up to the surface, bringing Remus with him. The air above the waves seemed strangely empty of sound to Remus’ ears without the constant swish of the sand.

“It’s all right,” Sirius reassured him. “They’re just reef sharks. They won’t attack us unless provoked.”

Remus nodded uncertainly, watching the gray shapes meandering below them in the water, doing his best to tread water without doing anything close to flailing. Seeing his dilemma, Sirius draped Remus’ arm around his shoulder so he could support them both with occasional lazy waves of his tail.

“You’re safe with me, regardless,” Sirius added, his tone softening. Remus looked back up at him to see his lips curving up into a small smile. “What do you think?”

He was clearly asking about the reef, not about the sharks, so Remus did his best to forget the predators circling below them and smiled back. “It’s incredible, really. Like nothing I ever imagined.”

Sirius beamed like he had just won first prize at a garden show, which Remus now understood wasn’t that far from the truth. This truly was _his_ reef, and if his careful attention to the coral was any indication, he spent most of his time tending to it in one way or another, like a British matron with her prize roses. The only real difference was that the reef, unlike roses, loved him back. It was also far more interesting than any English garden.

“I’ll show you one more place, then I’ll dump you back on land,” Sirius said, his arm drifting down to wrap around Remus’ waist, a band of warmth in the cooler water. His fingers curled around Remus’ side.

“Soon,” Remus requested. “Unless you were joking about not pissing in the lagoon.”

“I don’t joke about the nitrogen balance of my lagoon,” Sirius said, although the mischievous expression in his eyes said otherwise.

“Is that why you come onto land every day then?” Remus teased back, “To shit in the dirt?”

Sirius gasped as if affronted. “ _I_ am part of the great balance of nature, thank you very much.”

He tugged Remus back under, and they made their way back in the direction of the beach, still going at what Remus gathered was a leisurely pace for Sirius, just a bit faster than a human could swim. Remus let himself relax and watched the coral panning by below him. The diversity of species was truly incredible. Everywhere Remus looked he saw a fish, crab, or coral species he hadn’t seen yet. There must be thousands of different kinds of organisms here, and he gained a new respect for Sirius' marine knowledge. If what Sirius knew about barnacles was anything close to representative of his knowledge of the rest of the creatures in his reef, he must have a truly staggering memory.

Sirius brought him all the way to shore, but instead of depositing him on the beach, he dove down below the tide pools and led him through a wide opening into a sea-cave. It was impressively large considering the island as a whole was quite small, about the size of the first floor of Remus’ new lighthouse home. The water was mostly clear, but with patches of kelp-like seaweed in the corners, which seemed like they had been pruned into artistic shapes, like houseplants.

It wasn’t until Sirius brought him to the surface that Remus realized that was exactly what they were, because this was clearly Sirius’ home. The walls of the cave had been smoothed out, except for crevices carved into the stone in abstract designs, which were highlighted with strips of bioluminescent algae. A narrow skylight brought a beam of daylight down to an outcropping of stone that rose above the high-tide line. Sirius pushed Remus up onto this ledge and pulled himself up as well, so that they were sitting next to each other, water dripping off them. Hanging on the walls around them within easy reach were a variety of objects. Their craftsmanship was so distractingly fine that it took Remus a few minutes of looking to identify their purposes. There were several combs, unsurprising accessories for a merman with hair as long as his waist, and lying on a ledge next to them were two carved bone sticks and some smaller pins that Remus suspected were for holding up his hair in a bun. A large, perfectly circular mirror hung between the combs.

There were also knives of various lengths, and fine, filigreed baskets made of metal, presumably for tending the coral or collecting resources. There were no cooking implements or dishes, however, which confirmed Remus’ suspicion that Sirius ate his fish and crabs raw.

The tools were lovely and surely well-loved. Remus could only assume that the metal would rust in the damp, salty air if not polished and used regularly, and they all seemed to shine as if new.

There were also shells, each placed on their own shelf carved into the black stone, the reverence of their arrangement less like whimsical decorations in a beach house, and more like a display of family photos or even an altar. Some of them were quite large, including one abalone shell as long as Remus’ forearm. The iridescent glimmer of it reminded Remus of the shine of Sirius’ black scales underwater, and he almost reached out to touch it before remembering his manners.

“Is this where you sleep?” he asked, indicating the ledge they were sitting on, which seemed just long enough to accommodate Sirius’ body if he were to lie down. It was hard stone, but so was the sunning rock up on the surface.

Sirius laughed. “I sleep in the water. Usually there, in the seaweed.”

He pointed to the thickest clump of it, near the back hollow of the cave. It wasn’t what Remus would call a cozy arrangement, but he was no merman.

“This is just so I can eat without having half the food chain in here, trying to get in on the action,” Sirius said, gesturing to the ledge.

“And preen,” Remus grinned, pointing to the mirror and beauty tools.

Sirius rolled his eyes, “It’s called basic hygiene. I suppose you primitive humans haven’t invented it yet.”

“Of course. You wouldn’t want your fish to see you at anything less than your best.”

Sirius grinned, clearly not minding the teasing. “It’s not just fish anymore, though, is it?”

He didn’t give Remus a chance to process that statement, but just slid elegantly into the water. Remus took one last look around at the glowing cave, then he let Sirius grab his hand and tow him back to the beach.

+++

Sirius eased up on his restrictions about going in the water after that, enough so that after a couple weeks—and a few impatient lessons in swimming without flailing—he didn’t have any problem with Remus diving in on his own. It seemed that he really was just protective of the coral and all its inhabitants, so once Remus had demonstrated respect for the reef, he was allowed to experience it as much as he wanted. Sirius joined him more often than not, but it seemed to be more for company than because he thought Remus required supervision.

Remus had given up on focusing solely on barnacles and was now unashamedly sending back notes about fish, sea stars, and coral to the shipping company. There was just so much to see, and he couldn’t help wanting to learn about it all. He spent his evenings compiling his notes and adding illustrations in pencil or watercolor, as best as his no-nonsense style would allow. His art looked static and dead to his eyes compared to the vibrancy of reality. He was perpetually unsatisfied with it, but he kept trying.

Sirius seemed to love following Remus around the lagoon, frequently tugging him up to the surface to describe a rare species of fish or coral. His know-it-all attitude about the reef might have been annoying if Remus hadn’t authentically wanted to know everything too. As it was, he just couldn’t get enough. It was thrilling, actually. The shipping company had given him a two-year contract, but Remus had secretly hoped to stay much longer, perhaps even a lifetime. He had resigned himself to filling that lifetime with tedious experiments with barnacles, but instead he had an entire marine ecosystem to observe and document. It was enough work to keep him occupied indefinitely, and having Sirius around to learn from made it all so much better than he could have imagined. Remus still had the solitude he had been craving, as Sirius never ventured past the shoreline, but there was also the promise of company and learning whenever he wanted it. It was paradise.

A little more than two weeks after being given leave to explore, Remus was wading a few meters out when he noticed the tide was low, yet Sirius had not yet come to sun himself. Curious, he donned his underwater charms and dove down to peer into Sirius’ sea-cave. The entrance was wide enough that he didn’t have to go inside to see most of the interior, but what he saw confused him enough that he ended up swimming closer.

Sirius was clearly inside, suspended midwater and halfway obscured by the decorative fronds of seaweed, but he was curled around himself in a way Remus had never seen before. Possibly he was asleep, but he didn’t look at all relaxed. His face was obscured by the seaweed and his fluke, but his shoulders were knotted, and he shuddered, like a human might when feverish. Could merfolk get sick? Or perhaps it was a nightmare. Remus himself was plagued by nightmares, and the thought made his insides twist with empathy. Hesitantly, he swam through the entrance of the cave to investigate.

He had barely entered when Sirius jerked all over as if startled, and his body whipped out of its odd, balled-up shape, whirling to face Remus in a swirl of bubbles. They stared at each other for a moment, Sirius’ face as nonplussed as his own. Then Sirius scowled and shot forward, both hands outstretched, and pushed Remus bodily out of the cave, up to the surface, and out of the water so that he landed, sprawled, on Sirius’ sunning rock, which was almost directly above the cave entrance.

“What do you want, Remus the human?” Sirius stayed in the water below the rock, his expression deeply annoyed. He hadn’t called Remus that for weeks now, and hearing it again stung, even though it was no more than the truth.

“Sorry,” Remus mumbled, removing the underwater charms with a wandless command so he could see properly in the air. He wasn’t sure what he was apologizing for, but Sirius’ face made it clear that an apology was indeed in order. “I was just—just wondering where you were, I suppose.”

Sirius rolled his eyes. “I know you’re a helpless little thing, but surely you can manage to be on your own some of the time.”

“Yes, of course. Sorry.”

There was a moment of silence, then Sirius sighed and brought his arms up to rest on the smooth edge of the rock. His hair was currently held up in a high bun by the two carved bone sticks, which Remus had learned was the merfolk equivalent of bedhead. Maybe he had been sleeping after all.

“Well, I’m here now,” Sirius said. “What are you wondering about today?”

Remus racked his brain for something, sifting through the collection of questions that were always hovering in his mind or his notes at any given time. “Do you ever get any sea turtles or rays here? And…” He swallowed, now sure that he had invaded Sirius’ privacy, but also still concerned. “Are you all right?”

Sirius’ face twisted in a way Remus couldn’t decipher, and he dropped his forehead down onto his folded arms, shoulders shaking. Remus’ concern spiraled upwards for a moment until he heard Sirius laughing.

“I’m _fine_ , bottom feeder,” Sirius said at last, an idiom which Remus now knew meant someone was being incurably stupid, but he somehow minded it less than being called “Remus the human,” as it always seemed to be said with a grain of affection. After all, Sirius seemed to like the bottom feeders in his lagoon quite a bit.

Sirius raised his head and grinned up at him. “If you must know, I was on my way to having an orgasm.”

“ _Oh_ ,” Remus felt himself turning bright red, a shade which Sirius’ own brown cheeks couldn’t begin to imitate, even if they were a touch rosy at the moment. “I’m so sorry. I didn’t know.”

“Clearly.” Sirius smirked up at him and gave Remus an obvious once-over. “I always forget you humans can’t even reach your own dicks. Evolution can be so unkind.”

Remus frowned, a bit taken aback by this. “Of course I can—”

“Not with your mouth, you can’t.”

Remus’ eyes widened, and Sirius laughed, seeing Remus' gaze drop down, unwillingly, in the direction of the long, black tail under the water.

“Curious, little primate?” He leaned on the rock and swept his tail up out of the water, unashamedly putting the silver underside on display. Remus almost averted his gaze, but he was so used to seeing Sirius’ tail by now that it seemed odd to do so. There wasn’t anything to see anyways, just an area near the base of the fluke where the silver scales overlapped each other in a slightly different pattern. Remus thought of dolphins and quickly directed his eyes back to Sirius’ face.

“I didn’t mean to invade your privacy. I’ll be more careful in the future.” Although he wasn’t sure how he would manage that. It wasn’t as if Sirius’ cave had a door. He supposed he would just give the opening a wide berth.

Sirius seemed to be thinking along the same lines. “It’s not really your fault. You can’t exactly announce your presence like a normal person. Here.” Sirius dove down to the seafloor, splashing Remus on his way down, as was his habit. Remus was positive that it was intentional, too, since Sirius seemed perfectly capable of controlling his tail when Remus’ face wasn’t in the vicinity. Remus ignored it, as usual, and watched through the clear water while Sirius found a large, porous lava rock and brought it up to the surface.

“Throw that in, and I’ll hear it splash and fizz. That should be plenty distinctive enough.”

Remus nodded and helped place the rock-turned-marine-doorbell to the side of the sunning rock, where it wouldn’t get in the way. Sirius watched him, and then cast his gaze down, smoothing his hands over the sunning stone thoughtfully.

“Alternatively, next time you could always just come in.” He looked up at Remus through his eyelashes, silver eyes offering an invitation that was far more candid than the words themselves.

“You mean…for sex?” Remus asked, just to make sure he wasn’t misinterpreting this.

Sirius smiled, and for a moment Remus thought it had been a joke, but Sirius’ eyes, while playful, were positively radiating lust. He pushed himself up out of the water a little, straightening his arms so he was almost at Remus’ eye level.

“You must know,” Sirius said slowly, his eyes on Remus’ mouth, “our two species have a long history of…mutual enjoyment. There’s a reason they call it _getting tail_.”

This, Remus supposed, was the consequence of interrupting Sirius’ masturbation session. He leaned back slightly, giving Sirius a half-smile but not encouraging the attention any more than that.

“I do know that, but…” Remus licked the salt off his lips nervously, and then stopped when he saw Sirius’ eyes dart down to track the movement. “Thank you for the offer. I’m flattered. But I wouldn’t…enjoy it.”

Sirius raised his eyebrows. He didn’t lean in any more, but he didn’t lower himself back into the water either. “Don’t be so sure. I grew up in the shipping lanes, you know, and sailors get awfully randy. I’ve had experience with humans of several genders.”

Remus found this surprising—not the sexual experience bit, but that Sirius had apparently grown up out in the open ocean. It was odd to think of him away from this reef or any other. Sirius and the reef seemed to belong together so intimately that Remus had naturally assumed Sirius had been born here. The open ocean seemed empty and lonely compared to the cacophony of life in the lagoon that Sirius loved so much.

“I’m not questioning your skills,” he said, sticking to the matter at hand. “It’s just the way I am. I don’t tend to experience sexual attraction outside of the context of romantic relationships. Humans call it being demisexual.”

“Demi, as in half,” Sirius said thoughtfully, clearly making use of Latin nomenclature learned from taxonomical studies. He sighed, lowering himself back down in the water at last. “You humans have names for everything. You just love drawing lines in the sand, don’t you?”

That rankled a bit. Remus hardly felt as if his sexuality was a line in the sand, but he held his tongue for now. Sirius was still watching him, lips pursed as if he was trying to figure something out.

“Are you _sure_ you’re not attracted to me?” he asked at last. His tone was less sexual now and more genuinely confused. “I’ve seen you looking me over, you know. In fact, you do it quite a lot. If this is actually just some hangup about having sex with a Mer—“

“It’s not that,” Remus said quickly, feeling his cheeks start to heat again. He hadn’t realized he had been watching Sirius in such an obvious way. “I do—well, you have been observing what you might call an aesthetic attraction, which is not necessarily sexual.”

“An aesthetic attraction,” Sirius repeated. He narrowed his eyes, squinting up at Remus through the sun, which was getting brighter by the minute as the morning wore on. “So…you’re saying that you think I’m pretty?”

Pretty was not the first adjective Remus would have chosen, but looking down at Sirius now, at the strands of dark hair escaping from his bun, clinging wetly to his neck, and at his long tail drifting elegantly behind him in the water, it couldn’t be denied. Sirius _was_ pretty. He was gorgeous.

“Yes.”

Sirius smiled, as sudden and as bright as the sun coming out from behind a cloud.

“I can work with that. See you in a little while.” He winked and dove down under the surface, darting straight into his cave. He didn’t come out for almost an hour, and this time, Remus made sure to keep himself busy out of eyeshot of the entrance. 


	3. Sharks

**Summary for the Chapter:**

> Sirius brings Remus to meet his family. Merbabies, dolphins, and disaster.

A few days later, Remus was just finishing up his breakfast when he heard a strange cracking sound coming from the lagoon. When he went outside to look over the cliff, he saw Sirius in the lagoon below, slapping his fluke on the water.

“Get down here!” he called once he saw he had Remus’ attention. Remus sighed, left the dishes for later, and headed down to the beach.

“Get your clothes off and your charms on,” Sirius said as soon as Remus’ bare feet touched the sand. “We’re going on a trip.”

“Are we?” Remus raised his eyebrows but went ahead and removed his shirt. He was already wearing his swim trunks, having given up on trousers several days ago. He always ended up in the water anyways.

“Yes, to see my brother and his family.” Sirius was in the shallows on his stomach with his hands supporting his body, the waves swirling his tail to and fro.

Remus paused in the process of casting his charms. “There are other Mer around here?”

“Of course. They’re at the next reef over—around the island to the south.” Sirius saw his expression and smiled. “Did you think I was a hermit? There’s almost twenty people in our pod.”

“Oh!” Sirius had mentioned his brother before, but Remus had assumed he wasn’t nearby, as no one had come to the island in weeks. He put his hand over his eyes, taking in the open ocean beyond the reef. The island Sirius spoke of was not close. He could barely see it from here. “Maybe you should go on your own, then.”

Sirius swished his tail in the water impatiently. “I can bring you, don’t worry about it.” He saw Remus squinting at the horizon uncertainly and laughed. “Remus, it’s only a twenty-minute swim!”

“It will be longer than that with me along,” Remus reminded him. He was astonished, actually, that Sirius could make the trip in so little time, even on his own. He had underestimated Sirius’ speed.

“It will be fine,” Sirius said flippantly. “Unlike you landlocked monkeys, I can literally swim all day, so don’t worry about that. Now, come on. I haven’t seen them in weeks because I’ve been here watching you, and they can’t come to me because the baby’s too little.”

Remus felt a surge of mixed guilt and annoyance at that. He hadn’t realized Sirius was isolating himself just to guard the reef against mistreatment. “You can go without me, really.”

“And give you an opportunity to piss in the lagoon? Not a chance. I know you’ve just been biding your time.”

Remus was reasonably sure by now that this was a joke, but he still felt hesitant. He didn’t like the idea of Sirius dragging him along everywhere out of a lack of trust.

When Remus didn’t respond, Sirius sighed, looking at him with somewhat fond exasperation. “Remus, I _want_ you to come. Come see my family and the baby.” His expression turned cajoling. “They have sea turtles there. We might even see a ray or two.”

“Oh.” Remus felt his cheeks heating and gave a show of thinking it over some more, although truly his mind was made up. He was honored, actually, that Sirius wanted him to meet his family, so much so that he felt the need to downplay his reaction. “Well, I do want to see a turtle. I suppose the prospect is worth putting up with you for a whole day.”

“Rude!” Sirius laughed and swept his tail around, splashing Remus so hard he was almost knocked off his feet.

+++

Swimming with Sirius in the open ocean was nothing like swimming in the lagoon. Once they passed the drop-off, Sirius flatly refused to let Remus do any of the actual swimming at all. Instead, he tugged Remus down underneath him, holding him close against his chest to reduce the drag. It was surprisingly comfortable, with his back pressed against Sirius’ warm chest and Sirius’ strong, tattooed arms around him. He could feel Sirius’ body undulating with each push of his tail, and even with Remus slowing them down, they went much faster than Sirius ever bothered to go in the lagoon.

The open ocean was jarringly empty after the constant color and movement of the reef. Remus stared into the seemingly bottomless, dark blue water below him, feeling almost that he was looking up into the sky instead. The thought made him stiffen with an illogical fear of falling, and he held on to Sirius’ arms tightly until the vertigo passed.

They only saw a few fish: one solitary basking shark and a school of herring that Sirius took a detour to let him observe. These fish scattered when Sirius approached instead of swirling around him in greeting. Apparently his affinity with the marine life was the result of cultivated relationships, not a natural part of being what he was.

They had been swimming for what felt like around half an hour when Sirius started to swim closer to the surface, signaling periodically with his fluke. After a few more minutes, his arms tightened, and he started to trill. Remus turned his head to see Sirius’ face was bright with excitement, fixed on an unremarkable point in the bowl of blue that soon resolved itself into another merman, who was swimming out to greet them.

Sirius let Remus go and darted forward to meet him. They swirled around each other joyfully for a moment, not unlike the reef fish did with Sirius. Sirius had given him enough information at the start of their journey for Remus to identify the stranger as Sirius’ brother, James. His skin was darker than Sirius’, and he wore his hair in a multitude of tight braids that trailed down his back, each one weighted with a glass bead. His tail was a deep, rich red, shading to gold on the underside. There was no family resemblance at all, so Remus could only assume that “brother” was a less than literal term.

After a moment, James swam over to Remus and circled him as well. Remus smiled in appreciation to make up for the fact that he was too clumsy to return the greeting. James stopped in front of him, face close, and looked him over, trilling all the while. Remus glanced at Sirius, hoping for a translation, and then James’ eyes widened and he bobbed up to the surface.

“Sorry!” he said aloud once Remus had joined him. “I always forget humans are mute underwater.”

“I’m the one who’s sorry, believe me,” Remus said. It was very inconvenient not to be able to communicate with Sirius better when they were observing the reef together. Sirius had tried to teach him a few words, but Remus was a long way from even being able to separate the clicking and zipping into sensible sounds, let alone imitate them. He suspected he would never be able to do that very well no matter how he studied. As far as he could tell, the language was spoken at several times the speed of any human tongue, and it couldn’t be slowed down easily without changing the meaning.

He had assumed, at first, that he wouldn’t be able to communicate with James and Lily at all. There didn’t seem to be much reason for merfolk in the middle of the Pacific Ocean to know English. It was a miracle, actually, that Sirius spoke the language so well. Apparently he had learned from sailors and marine biology textbooks. But when Remus had expressed his thoughts on this to Sirius, he had just shrugged.

“James is on the council, and they communicate with humans all the time. He speaks about a dozen human languages, and he taught Lily and me too. It's not like it's hard.”

That was a statement Remus had never heard expressed by an English language learner ever, and he supposed it went to show that the Mer language was indeed on a whole different level of complexity.

Here and now, Sirius lifted his head above the surface and pulled Remus' arm over his shoulder to help him tread water in the ocean swell, a maneuver that Remus was so used to by now that he hardly noticed it.

“James, this is Remus, a human who moved himself onto my island, theoretically to study barnacles. Remus, this is my best friend and brother, James. You can call him Prongs if you like.” He grinned. “Show him why, James.”

James laughed and flipped over in the water, pointing his tail to the sky so that Remus could see that where Sirius had one spike at the base of his fluke, James had two.

“You didn’t show him the other two!” Sirius protested, laughing, as James resurfaced. James stuck his tongue out at him.

Sirius turned to Remus, “For your reference, we usually have one hunting spike, but occasionally there‘s an _urchin_ like James here—”

“You're just jealous,” James interrupted, smiling lazily as if he was used to having this particular interaction with Sirius.

“—and in all cases, the dorsal and the ventral sides match,” Sirius finished, grinning wickedly when this made Remus blush. Although, he wasn’t sure if it made sense to be embarrassed at all, as it was clear neither James nor Sirius considered this information private.

Sirius went on to say, “And, yes, I’m actually quite jealous. He doesn’t even make good use of it. Never had a threesome in his life.”

James laughed and swept his tail up to splash Sirius—and, by virtue of proximity, Remus—in the face. “Come on, you dab, let’s go. Lily and Hari are waiting. Remus, are you ready to meet the most beautiful mermaid and the most adorable baby in all world’s seas?”

“Definitely,” Remus said, smiling at James' sincere good cheer.

“Perfect, but first, we have some reef rules.”

Remus hid a sigh. He wondered if everyone got lectures before going to a new reef, or if it was just the human visitors. Probably the latter.

“I'm going to tell you right now that when I say my wife is the most beautiful mermaid in the ocean, that is an actual, objective fact. She is also the most clever, kind, and talented person you'll ever meet. Here, see? She made these for me.” He held out a few of his braids for Remus to inspect, showing off the glass beads, which were the same red and gold as his tail. “This one was for our anniversary, and this one—”

“Prongs!” Sirius interrupted. “What does this have to do with your reef rules?”

“Oh, right. So anyways, that’s all just to say that the most important rule might be difficult to follow, but it is _imperative_. No matter what happens, Remus, you have to promise me, you have to _swear..._ you will not fall in love with my wife.”

Sirius groaned and flopped backwards into the next swell, raising a huge wave with his tail that engulfed James' head. Remus laughed, quickly moving back to treading water on his own.

“I promise,” he said once James had re-emerged.

“Good. Okay, let’s go!” James sank down in the water almost all the way and then bobbed back up to add, “Oh, and don't touch the coral.”

“He never does,” Sirius reassured him. He wrapped his arms around Remus' chest again, and for a moment, with his mouth near Remus’ ear, it felt much more intimate than it had before. Then Sirius pushed them both under and began swimming, towing Remus along beneath his body, and the strange instant of intimacy vanished, overshadowed by practicality.

They continued on, the two mermen clicking away at each other nonstop, clearly catching up. The reef wasn’t far, as it turned out. It only took a few minutes for it to emerge from the blue. At first it was just a dark shadow, but gradually, it bloomed into colors just as impressive—if not more so—than those of Sirius’ reef.

Hovering midwater near the drop-off was a mermaid with bright red hair that stood out like a spotlight. In her arms was an infant—who was struggling mightily to be released—that looked like a tiny version of James. Once Lily saw them coming, she let the baby go, and the child went streaking across the gap to crash headlong into Sirius’ arms, which he had emptied of Remus in preparation.

Before they left the lagoon back home, Remus had asked Sirius about Hari’s gender, just as he had asked about James and Lily’s. He had received a lecture about how parents should wait until their children were old enough to declare their gender instead of just _deciding_ , with some scornful lines thrown in about humans being obsessed with genitals, and couldn’t they just leave children alone to be themselves? So it was that Remus learned that apparently all merfolk were gender neutral until they self-declared otherwise. Hari was just under a year old, too young to talk—although apparently they did babble in the merfolk language, which Sirius had assured Remus was adorable—so they didn’t yet require gendered pronouns.

The baby trilled with delight at seeing Sirius, and made a quick swirl around Sirius’ head in imitation of the greeting Lily gave him a moment later.

Lily was, unlike the other two, pale-skinned, and her nudity was much more obvious than the mermens’, for obvious reasons. Her breasts floated serenely in the water, spherical in a way that Remus wasn’t used to seeing—not that he could be said to be used to seeing breasts at all. It was clear, now more than ever, that merfolk didn’t even have a concept of nudity, however, so he tried to take it in stride.

Lily’s tail was green, shading from dark emerald on the dorsal side to pale seafoam on the underside, the perfect foil for her bright orange hair, which drifted around her head, loose, like Sirius usually wore his. Her eyes were the same vivid green as her tail.

This eye color was shared by her child, who had now finished circling Sirius in delight and had spotted Remus. The baby darted behind their mother’s shoulders, into the cloud of her hair, and peered cautiously at the newcomer, rather like a fish hiding in the tentacles of an anemone.

Aside from the eyes, Hari looked like their father. Their skin was dark brown, and their hair was a thick, curly cloud of black. The red and gold tail matched their father’s as well, although it was much shorter and had the same baby fat as the rest of their body. Hari was clearly not yet as adept a swimmer as James or Lily, but the child still moved more skillfully than a human of a similar age might on land.

James and Sirius were still apparently quite excited to talk to one another, and once the four of them were back over the reef proper, it was Lily who pulled them up to the surface so they could be verbal again.

“Welcome, Remus,” she said, apparently having heard his name from the others underwater. “Hari, this is Remus. It's all right. He lives with Sirius.”

Remus didn’t bother to correct the slight mistake in that sentence, instead smiling at the baby, who was now hiding in Sirius’ hair. Hari poked their head up out of the water cautiously, Sirius’ wet hair clinging to the baby’s head more than it would underwater.

Sirius and James had gravitated towards each other as soon as they reached the surface, and Remus watched, a bit surprised, as James’ tail drifted over to wrap around Sirius’, until their flukes were pressed flat against one another, underside to underside. Lily joined them, seeming to think nothing of it, and after a moment she reached out for Remus and pulled his legs into the tangle as well, until they were all wrapped around each other like seahorses around blades of underwater grass. They all sat back a bit in the water, their joined tails providing the counterbalance, until it was almost like being seated around a dining table.

After all the discussion of prongs and such, this made Remus even more self-conscious than Lily’s bare torso, but after a few minutes he began to realize the practicality. Wrapped together like this, they could easily stay at the surface with just the occasional mutual beat of their entwined tails, and it kept them tethered close enough to each other to converse over the sound of the waves on the distant shore, which crashed more dramatically here than in Sirius’ lagoon.

“Don't worry, little guppy,” Sirius soothed, reaching around to cradle Hari. “I know his legs look knobbly and bizarre, but they aren’t sharp. Jump?”

He held the baby up in midair, and Hari immediately started to wiggle and coo with excitement. Sirius grinned and threw the child bodily away from them. It would have been an insane thing to do on land, but here in the water it was clearly a favorite game. Hari sailed through the air and into the water with a splash and came zipping back for another repetition almost immediately.

Lily asked Remus some polite questions about barnacles while Sirius continued to hurl Hari in various directions, until the baby appeared to grow tired and wriggled into the center of their huddle to snuggle and nurse. Once Hari had drifted off, James pulled the baby into his arms and disentangled himself to float on his back, letting the child sleep on his chest in exactly the same way as otters did with their young.

Sirius saw Remus observing this and grinned. “Would you believe that Remus showed up here knowing absolutely nothing about the Mer? He even…”

He paused for a second and then lowered his head halfway into the water to continue in the Mer language, smiling wider than ever.

James rocked in the water as he burst into laughter, although he quickly quieted down and soothed Hari back to sleep.

“Sirius!” Lily smacked him lightly on the head. “You’re being rude. Stay verbal, or I’ll repeat everything you say.”

“I’m pretty sure I already know what he‘s saying.” Remus sighed and shifted his legs nervously where they were pressed snugly against Sirius' tail. He was sure Sirius was relating the tale of being interrupted the other day. “I thought you were having a nightmare!”

“I do get nightmares,” Sirius said quickly, then followed this up with a sly look. “You‘re still welcome to come wake me up from them whenever you want.”

Lily rolled her eyes and let Sirius go with a little push of her tail. “Come on, Remus. Let's leave these two to their immaturity. Sirius said you wanted to meet our sea turtles?”

Remus accepted this offer gratefully. It was a bit irritating that Sirius was continuing to flirt, even jokingly, after Remus had already explained how his sexuality worked. Sea turtles would be a welcome relief.

Lily spent several hours showing him the stately giants and then giving him a tour of the nearer parts of their reef. Their reef was much larger than Sirius' and surrounded most of the island. Unlike Sirius, Lily was patient enough to let him swim on his own. It was more polite, to be sure, but Remus found himself missing Sirius' speed and the companionable hand-holding. It was also much more tiring. Lily was very kind, however, and, unlike Sirius, didn’t make any comments about his supposed-inferiority as a human.

She also showed him her workshop. Like the place Sirius slept, it was in a sea-cave, but this one was much larger, with multiple ledges carved around the edges for her to sit on while she worked, and a huge selection of tools for metalworking, woodworking, and the glass-making equipment James’ hair decor had implied. It was all arranged to be within easy reach of someone who never stood up, and it reminded Remus of a kitchen designed to be useful to someone in a wheelchair. There were a few examples of her work on the walls, and they were all truly impressive feats of craftsmanship.

After a while, Hari swam over to them to nurse again, darting back to the distant figures of James and Sirius right after. Apparently Hari was allowed to roam freely within the confines of the reef, which surprised Remus because he had already seen several species of shark here. Perhaps, as resident merfolk, they simply didn’t have to worry about such things. Sirius didn’t seem to worry about his sharks much either.

Lily came up to the surface often to speak, and she wrapped her tail around his legs every time. It was clearly a social norm, and after a while Remus hardly noticed it anymore. He wondered if it was Sirius' extra experience with humans that had prevented him from doing it before.

Lily also sang much more than Sirius did, and seemingly with more ease and pleasure. Where Sirius was usually content to zip and trill away at the creatures of his lagoon, Lily more often than not hummed quietly instead, in an almost absent-minded way. Remus attributed this to the size of the reef. Singing seemed to be the main way merfolk did magic, and with such a large reef to nurture, Lily and James must need to work harder than Sirius to achieve the same effect.

By the time James and Sirius rejoined them, Remus had forgotten about his irritation with Sirius entirely. He also found himself longing for the comparative simplicity and quiet of their island. The reef back home wasn’t large enough to get lost in, unlike this place. He was relieved when Sirius finally announced it was time to head back.

After a lengthy parting, they started back across the open water. Sirius swam slower this time, apparently in less of a hurry now that he had finally had a chance to spend time with his family. They were about what Remus judged to be halfway when Sirius slowed in the water, stilling himself as if listening. Then he smiled and bobbed up to the surface just long enough to say, “We’re going on a little detour.”

“I’m getting a bit tired,” Remus started to say, but Sirius shook his head insistently.

“You won’t be sorry. Trust me. And it’s not far.”

He changed direction, and, true to his word, it was only a few minutes before Remus started to hear what Sirius had. The ocean was _full_ of trills and clicks, as if there were an entire crowd of merfolk just up ahead. The thought of meeting more people when he was already tired made Remus’ head ache, but when the first swimming figure materialized out of the blue, it wasn’t one of the Mer at all. It was a dolphin.

Soon the whole pod of dolphins had surrounded them, sweeping past Sirius and appearing to return his speech. The sleek gray bodies spun around them at intimidating high speeds, but they certainly seemed friendly. A few of them slowed down to peer at Sirius more closely. Sirius left Remus on his own for a bit so he could swim with them, imitating their jumps and spins with laughing joy.

After a couple minutes, Sirius surged up underneath Remus, bringing his head to the surface.

“Can you speak to them?” Remus asked.

Sirius shook his head, smiling and ducking back under the water every second or so to see and hear the dolphins. “Not really. It’s different. Do you want to ride one?”

“ _Ride_ one? How?”

“I’ll show you!” Sirius grinned and found his hands, then pulled him down under the water. He clicked cajolingly until a dolphin came near enough to touch, then carefully placed Remus’ hands over the dorsal fin. He put his own hands over Remus’ own, wrapping himself securely around Remus’ back and effectively pinning him, and then trilled, sliding his tail quickly along the dolphin’s side. Something about this must have inspired the dolphin to move, because suddenly, they were. The creature shot through the water at an incredible speed, diving first down and then turning and making a break for the surface. Remus had just enough time to see the silver of the surface rushing towards them, and then suddenly they were up in the air, all three of them flying free above the water for one instant—just long enough for Remus to gasp and Sirius to cheer—and then they crashed back down into the water.

Remus would have fallen off then, but Sirius’ grip was sure. The dolphin jumped them again, and again. It was exhilarating, and Remus forgot all about being tired.

They rode with the dolphin a considerable distance until a final jump dislodged even Sirius’ strong arms, and they went tumbling together back into the water.

Remus gasped again, underwater this time, as pain flared along his lower leg like someone had struck a giant match along his calf. At first he thought it was just the slap of the water hitting him at an unlucky angle, but the pain didn’t go away. He struggled in the water for a moment, horrified to see the bloom of blood, to feel the sharp protests from the sliced muscles that didn’t want anything to do with swimming. He didn’t understand what had happened. If he hadn’t known better, and if the shape of the long, thin gash hadn’t been all wrong, he would have thought one of the dolphins had bitten him, but that couldn’t be it. The dolphins were all swimming away by now, and they hadn’t been aggressive.

Sirius was there an instant later, pulling him above the surface, his face just as shocked as Remus’ was.

“You—you’re bleeding!” Sirius gasped. “You hit my spike!”

Remus nodded, teeth gritted, now understanding. He must have tangled up with Sirius’ tail when they had fallen off the dolphin. He had never touched Sirius’ spike before and was surprised that it was sharp enough to do this much damage so quickly.

“You’re _bleeding_ ,” Sirius repeated insistently. “You have to stop!”

His tone was urgent but not unreasonable, as if he actually thought Remus could will his body to comply.

“I-I can’t,” Remus said at last, bewildered that this wasn’t obvious.

“Yes, you can!” Sirius shook him a little. “You’re a wizard! Use your magic!”

“I _can’t_ ,” Remus repeated. “Not without my wand!”

He never brought it with him when he went in the water. The risk of losing it seemed too great, and it would be very difficult to get another. He needed it for growing food and other land-chores more than he needed it for the quick convenience of using it while swimming. Or so he had thought.

Sirius’ eyes widened in realization and he dove down, grabbing Remus’ leg by the ankle. Remus gasped with renewed pain as Sirius pressed his hands over the gash, as if he would will it closed. Remus could just barely hear a few notes of Sirius singing. He must be trying to use his magic to heal the wound. Remus did his best not to struggle, but the pain didn’t ease. After a moment Sirius let go and resurfaced, scowling with frustration.

“I can’t either. Fuck!” Sirius put his hands to his head for a moment, pressing hard, and looking around the ocean in different directions, as if for inspiration or making a decision. “It—it’ll be okay. We just have to keep moving. We’re not too far from home.”

“Sharks,” Remus said, because they were both thinking it. “You—you can swim faster than a shark, right?”

“Yes.” Sirius swallowed, his silver eyes meeting Remus’ with an uncharacteristically burdened expression. “But not with you.”

“But you—you said I would be safe with you regardless!” Remus protested. If he had known the danger was so great, he would have done more, would have brought some sort of tools to deal with this potential problem.

“You will be!” Sirius said, his expression suddenly fierce. He seemed more determined than confident, however, and he didn’t say anything else. He just swept Remus back into his arms again and started to swim.

Remus had thought Sirius was going fast before, but it was nothing compared to this. He could feel the water dragging along his body as Sirius undulated above him, the ocean trying to drag them apart. Sirius’ arms stayed tight around Remus’ chest, though, refusing to let go. Remus tried to hang on to help him, but he was already getting dizzy with pain. He couldn’t tell how quickly he was losing blood. He hadn’t even really gotten a good look at the wound.

It was nerve-wracking, swimming through the endless bowl of blue that seemed much more frightening now than it had this morning. Remus couldn’t help with the swimming at all, so he spent the time frantically scanning the water instead, looking for any sign of approaching sharks. He kept reminding himself how barren the open ocean was, how statistically unlikely it was that a shark would be near enough to sense the blood. It was like Sirius said, as long as they kept moving, they should be all right.

Finally, Remus saw the shadow of the reef emerging ahead of them, like a mountain rising abruptly from the distant seafloor. Remus felt his chest go weak with relief, welcoming the sight of the darting fish and the coral slowly showing its color as they drew nearer.

Sirius, however, was gripping him tighter than ever, and he clicked rapidly in a tone that even Remus could recognize as anxiety. They were almost home, but Sirius was still afraid. It took a few more seconds for Remus to understand why, as the shapes prowling around the outer edges of the reef became clear.

The open ocean was mostly devoid of life, and thus relatively safe, but the reef wasn’t. The reef _always_ had sharks.

Remus dug his nails into Sirius’ arms, trying to will him to turn away, but he knew it was foolish. One way or another, they had to get to land, and in this part of the world, land meant coral, and coral meant sharks. They had no choice but to risk it, and it was better to do it now, while Sirius was not yet tired and Remus still had some blood left, than try to make it back to James and Lily, or to some other nameless island. This was also where Remus’ wand was, and he would need it to heal himself.

Sirius shot forward at what was clearly the top speed he could manage while still hanging on to Remus, aiming for a gap in the scattered shapes of the predators. He was moving so fast, Remus thought for sure they would make it, but then another shark loomed out of the coral directly in front of them. It was one of the smaller, less aggressive, white-tipped variety, but it moved with intent, clearly already aware of the potential meal headed its direction.

Sirius backpedaled frantically, sweeping his tail around to knock the white-tip with the edge of his fluke, and tried to swerve around it, but the delay cost them dearly. Remus saw movement out of the corner of his eye and turned his head to see the larger, more dangerous, black-tipped sharks approaching, their speed seeming to increase exponentially the closer they got. They moved with the single-minded determination of a wolf pack but without the coordination and caution wolves showed, each one caring only about themselves and filling their own stomachs.

Sirius tried to dodge through a narrow opening between them, but the white-tip had recovered and filled the opening—or perhaps it was a different one of the same variety. All Remus could see was that they were surrounded.

Sirius let go of him abruptly, freeing himself for greater maneuverability. He brought his tail up protectively. His fluke, fins, and spike all flared wide in warning, but the sharks didn’t even seem to notice. As soon they were close enough to do so, they moved in without hesitation.

 _Frenzy_ , Remus thought, his mind awash with terror and adrenaline as the water around him erupted into movement and bubbles. Sirius was swimming around him in a fiercely protective spiral, his tail moving almost too fast for Remus to see as he lashed out at the sharks over and over. They kept coming, however, a seemingly endless wall of white underbellies and mouths full of teeth. There seemed to be dozens of them—more than Remus had thought lived in the reef at all.

Sirius bashed them aside in groups with his tail, but they just came back, hardly fazed, and Remus realized with dismay that Sirius wasn't using his hunting spike at all. He didn’t want to hurt them.

His movements were rapidly slowing, however, and the flashes of his face Remus saw showed he was dissolving into a panic. This wasn’t a fight he could win, not without either abandoning Remus to his fate or killing the sharks, and he was clearly unwilling to do either.

Suddenly, Sirius' body convulsed, arching, and Remus saw blood bloom in the water, flowing from a point on Sirius' back where a shark had managed to get close enough for its teeth to scrape along his skin. At almost the same instant, Remus felt a hot, ripping sensation on his leg as another one got past Sirius’ guard. He shouted, the sound coming out as a muffled explosion of bubbles.

Sirius whipped around to see what had happened and batted the shark away from Remus’ leg, his silver eyes wide and full of panicked dismay that was so intense, so devoid of reason, that it looked distinctly inhuman.

An instant passed, and then Sirius lunged forward, grabbing both Remus' hands and sealing them tight over his ears, pressing down painfully hard. He yanked Remus in close so his face was pressed against Sirius' chest, right at the center, where the star of Sirius’ namesake was inked as a single, lonely dot, from this perspective oddly distant from all the other marks around it. 

No sooner had he drawn Remus in than the pain started, a vise that pressed down so suddenly, so viciously, that at first Remus thought Sirius was trying to crush his skull. But the pain wasn’t coming from Sirius' hands, although they were still pressing Remus' hands to his ears. Sirius was singing.

It was a sound wholly unlike any Remus had heard from him before, somehow both high and low in tone at the same time. Like the merfolk language and the small, humming spells Remus had seen Sirius cast on the coral a few times, it seemed to come from some lower part of his throat that didn’t need air, and the pain in Remus' head came not from anything physical or even from the frequency of the sound, but from the magic embedded in it. It was a huge, endless thing, as if the whole of the ocean had condensed itself into Sirius' voice, the pressure of an entire planet‘s worth of water localized to this small area, with the mindless intent of crushing everything alive.

Remus didn’t know how long Sirius sang for. He was only aware of the movement of the sharks slowing around him, his vision blurred by the blood swirling from his nose as he slipped into a state of near-unconsciousness. He distantly felt the tug of water around him but didn’t recognize it as a sign that Sirius had started swimming again until there was sand under him, scraping at his knees and arms as Sirius hauled him out of the water and onto the beach.

He lay there for several long moments, trying to adjust to the strange sensation of breathing in air once again, the setting sun casting a dim wash of light over everything. The whole world seemed bizarrely still after the hurricane of the frenzied sharks, as if time had stopped.

When he finally got the strength to lift his head enough to look around properly, he saw Sirius nearby, fully out of the water and several meters from the waves. Remus had never seen him so far from the ocean before, and a bolt of concern filtered through the haze of exhaustion and discomfort.

Sirius dragged himself even further up the beach, his tail moving out to the side to propel himself forward like a sidewinding snake until he could reach far enough to scrabble in the rocks above the tide line. Remus closed his eyes for a moment and then opened them when he felt Sirius wrapping his fingers around his wand. He was saying Remus' name.

“ _Remus_ , come on! You have to do it, I don’t know how!”

Remus groaned and clutched his wand. He took another moment to gather his strength and then rolled to his side so he could see the wounds on his legs and cast the charms necessary to heal them. By some miracle, he didn’t mess it up, and some of the pain eased. His head was still throbbing, however, although his nosebleed appeared to have stopped on its own.

“I think I have a concussion,” he said breathlessly, looking around at the distorted, blurred view of Sirius’ concerned face and the beach beyond. Then he recognized the effect. “Oh, no, it’s…”

He didn’t bother to finish but just said the words to lift the underwater vision and breathing charms, sighing with relief when his eyesight returned to normal.

“Are you all right?” Sirius demanded, his voice shaking. He was running his hands over Remus’ head. “Your ears are bleeding.”

“Eardrums,” Remus agreed. He didn’t know the specific charm for healing that, but he performed a basic healing charm anyways, and the pressure in his head lifted a bit. He took a steadying breath. “I’m all right.”

Sirius exhaled heavily in relief and slumped down, held up only by his elbows, his forehead sinking into the coarse, black sand. Out of the water, his hair looked stringy and flat, and it clung heavily to his arms and shoulders. From this angle, Remus could see the long gouges the shark had left on his back. Strangely, they weren’t bleeding, and they seemed to be slowly knitting themselves back together, which explained Sirius’ confusion at Remus’ inability to heal his own wound.

After a minute, Sirius pushed himself up onto his hands and looked back at the lagoon. Whatever he saw there made him moan in dismay, his expression such pure, distilled misery that Remus could hardly stand to look at him. He followed Sirius’ gaze and saw the pale body of a shark rolling lifelessly in the waves.

Sirius was already crawling and sidewinding away, his lack of grace on land utterly foreign and strangely heart-wrenching when Remus was by now used to seeing him underwater, in all his glory. He watched, feeling Sirius’ pain as if it was his own as Sirius went out into the lagoon and brought back, not just the body of that shark, but another, and another.

Soon the little beach was nearly full of their gray, drooping bodies, which looked pale and bloated against the black of the sand, as if they had been dead for days, not minutes. There were about a dozen, far fewer than they had seemed in the panic of the feeding frenzy, but still enough that Remus felt a sinking certainty that none of the lagoon’s sharks had survived. That much was also obvious from how intact the bodies were. They had been dead for at least twenty minutes, perhaps longer, depending on how long Remus had been unconscious, and no other sharks had come to feed on them. The lagoon’s many other, smaller piscine carnivores had not tried to eat them yet either. Aside from the waves themselves, the whole lagoon seemed silent and still, as if all the life had been scared into hiding by Sirius’ song.

Remus was exhausted, thirsty, and hungry after a full day of swimming and danger, but he didn’t leave the beach. He summoned some water and food and made do, trying to compose himself so he could offer some comfort, if it was possible. Sirius was clearly deeply distraught. His face grew more ashy with every body he pulled from the water, and by the time he had laid out the last shark and sat himself in the low waves near its lifeless, gaping mouth, he was shaking all over with fatigue and misery, tears of true grief running down his cheeks.

When he spoke, however, his voice was dark, the anguish hidden behind a thin film of something much more bitter. “I hope you humans eat shark.”

The phrase “you humans” was ugly in his mouth, and his eyes wouldn’t meet Remus’ own, instead staying fixed on the line of bodies on the beach.

“No,” Remus said quietly. “I’m sorry.”

Sirius growled with frustration and his tail twitched suddenly to life, slapping the water behind him. “At least help me clean them, then. I’m not going to let them rot!”

He surged away into the waves, returning a minute later with some of the knives from his collection in the sea cave. He shoved one across the sand in Remus’ direction. The finely wrought blade kicked up sand as it went, coming to rest near Remus’ outstretched hand. It was a beautiful tool, the handle carved into a smooth, practical shape, with designs etched into it to give traction and a sense of life. Perhaps it was one of Lily’s designs.

“I can do it with magic, if it’s all right,” Remus offered hesitantly. He was afraid he would mangle the work if he tried to do it manually, but he had practiced the charms needed many times this month, every time Sirius brought him a fish to eat.

“Fine.” Sirius dropped his knife and scooted backwards. He watched, face an impassive mask, as Remus cast the charms for cleaning and skinning on each one of the creatures. The carnage was truly horrific, but it was clear that in Sirius’ eyes this was better and more respectful than throwing the bodies away. Remus was vaguely aware that there were parts of them that were useful, the skins in particular, and perhaps the teeth as well.

As he was finishing, Sirius gestured to Remus' wand, voice still sharp and bitter, “It's not such a bad tool, then. If you have it on you.”

Remus sank to the sand, feeling the words like a blow. “I should have brought it. I’m so sorry, Sirius.”

“No, you aren’t!” Sirius' tail lashed through the water, the fins drawn in tight, like when he was hunting. “You can’t be sorry, not really, because you have _no idea_ what you’ve done!”

“I know the sharks are important for the reef.” Remus tried to keep his voice quiet and calm, to balance out the unstable rise in Sirius'.

“You don’t know anything!” Sirius cried, his hands fisting in the sand. “You came here knowing nothing, and you still know nothing! Do you have _any_ idea how hard it is to keep a reef alive when you—you _humans_ are overfishing and acidifying the ocean and making temperatures rise and dumping anything you can reach into the water every chance you get? It’s like you ruin everything you touch—everywhere you go you throw things out of balance!”

Remus winced, unable to counter these accusations, even though he, as an individual, didn’t carry much responsibility for them, if indeed he carried any at all. As a wizard, he had workarounds for most of the things muggles did, like driving cars, that caused the horrors Sirius was listing.

“And now you’ve done it here too!” Sirius continued. His voice was loud with mixed fury and self-blame, horrible to hear. “You’re not supposed to _be_ here, you aren’t part of this system! I should never have let you stay!“

Remus couldn’t stop the pain of those words from reaching him. Ever since he had arrived, he had done everything Sirius had asked, no matter how ridiculous it had seemed. He cared about the reef too. He wasn’t here to exploit the ocean or do any of the other things Sirius was talking about. He just wanted a place to be.

He still hadn’t told Sirius why. He hadn’t told him about the transformation that was now less than a week away. There just hadn’t been a good moment. Maybe there was never a good time to tell your one and only neighbor that you were going to be turning into a monster once a month. But he would have to do it soon….assuming Sirius didn’t try to force him to leave.

The thought made Remus feel heavy and lifeless. This place wasn’t just a nameless, isolated island to him anymore, a place to disappear. It was home. The lighthouse full of his scientific notebooks and drawings was home. The reef and everything in it—especially Sirius—was home. He couldn’t imagine living anywhere else. Where else in the world was there a whole lagoon full of life to study, and a lovely and loving person to share the joy of it with?

“I’m glad you did let me stay,” he said, still trying to keep his voice gentle, but there was a shake in it. He reached out, tentatively, and put his hand around Sirius’ own, which was still clenched viciously in the sand. Sirius’ skin was sticky with shark blood. “This is terrible. But it will get better, Sirius. More sharks will find the reef—“

“You still don’t understand!” Sirius shouted, snatching his hand away. His voice was just as furious as before, but he was also crumbling around the edges, as if he was dangerously close to sobbing. “There isn’t going to _be_ a reef anymore!”

With that, he shoved the rest of his body away as well, propelling himself into the water, leaving Remus on the beach with the sharks, confused, exhausted, and alone.


	4. Tuna

**Summary for the Chapter:**

> Feelings and the full moon.

The sharks were rotting.

After Sirius stormed off, Remus had gone up to the lighthouse to pass out, and when he came down later the next day, he was disturbed to find the carcasses of the sharks just as he had left them. Birds and other small scavengers had made a considerable dent on the bodies. Thinking Sirius must still be asleep as well, he just cast cooling charms and wards on the meat to keep it fresh and undisturbed and went back up to the house. His headache from being in range of Sirius’ deathly song hadn’t fully gone away, and even the short walk back up to the lighthouse was exhausting.

On the second day, however, he started to feel better and therefore had the energy to worry. Sirius was nowhere to be seen. Remus was used to looking out the lighthouse windows and seeing the merman’s dark shape silhouetted against the coral or lounging on the sunning stone, but as far as he could tell, Sirius hadn’t come out of his cave at all. After what had happened, Remus wasn’t surprised to see that Sirius wanted space, but Sirius had seemed adamant about not wasting the shark’s meat. It was concerning that he hadn’t come to tend to the bodies.

The thought of Sirius avoiding him with such determination was truly depressing, even if it was somewhat expected. Remus understood that he had upset the balance here, but he had come to think of Sirius as his friend, and the lagoon seemed empty and lonely without him.

The idea of studying the reef on his own was uninspiring, so Remus spent the day inside, trying to work. If Sirius needed space, he could offer that. He had observational data to analyze and drawings to finish.

It was the drawings that ended up taking up most of his attention. His skills were still not what he wanted them to be. He wanted to be able to capture the nuances and vibrancy of the reef he had come to love, which was so unlike these flat, drab drawings. He did what he could, filling in the shadows, adding extra shading to the colors of seaweed, the fins of the fish.

He found himself drawing Sirius as well. At first it felt uncomfortably voyeuristic. Sirius wasn’t a _creature_ , here for Remus to study and send reports about. He was his own person. Yet, it was his image that seemed to fill Remus’ mind much more than the other sea life. He drew the flare of Sirius’ fins, showing how the strong webbing gradually tapered into translucence, and added variations for the different positions Sirius could move them into, with notes about the emotional state each position reflected.

He drew Sirius’ hands, with their strong fingers and unique webbing. He drew them flexed, as they were when he swam, and gently cupped, as they had been when he sang to the coral. That memory inspired him and he filled in the rest of the scene, carefully sketching the lines of Sirius’ face, his relief and joy at the coral’s recovery. He even drew the eel, watching from below.

Another drawing started with a different angle of Sirius’ hands and became an entire family portrait: Sirius holding, with unfeigned appreciation, a small, unremarkable crab that Hari had brought to him as if it were a trophy. Lily and James looked on from the background, and Sirius’ gaze was fixed, not on the crab, but on the baby, eyes full of love.

There were many more. He drew Sirius as he had first seen him, sleeping in the sun. He drew Sirius with the dolphins, Sirius floating on the surface of the lagoon, Sirius in the midst of a school of welcoming, swirling fish. There was so much in his mind, his hands could hardly keep up. He sketched drawing after drawing, pausing only briefly to add swirls of watercolor when he just couldn’t stand the emptiness otherwise.

The details of Sirius’ form, his colors, his expressiveness…they were easy to put to paper, much easier than drawing some unintelligent fish or a lump of coral. As Remus drew, it was clear that, while in theory he was on this island to observe barnacles and other marine life, in practice, it was Sirius who had captured his attention. Remus had memorized every inch of him without even trying, without even noticing he had done so.

It had to mean something. What, exactly, was ludicrously obvious when he looked at the portrait of Sirius with the crab, at the light in his eyes, the gentleness and adoration in his expression. Part of Remus wanted to be that crab. He wanted to be held safely in Sirius’ hands, protected from the horrors humanity would unleash on coral reefs, werewolves, and anything else they didn’t understand. He wanted to stay here. He wanted to be part of the island, part of the reef, part of Sirius’ life.

He slept restlessly with these thoughts swirling in his mind, and overnight it all coalesced. In the morning, he woke early and began one more portrait, one that seemed both the answer to his feelings, and the thing that stood in the way. He drew Sirius and himself, surrounded by sharks with gaping, hungry mouths. In the portrait, as in his memory, Sirius held him close, hands cupped protectively around his head. His face was an agony of pain and determination as he sang the sharks into death, as he saved Remus’ life despite the unbearably high cost.

Remus took his time with that one, filling in all the colors of the ocean and the coral below. He painted the dark caverns of the shark’s mouths and his own brown hair and glaringly out-of-place green swim trunks. He used his finest brush for the lines and dots of Sirius’ tattoos, allowing each piece of the moment to form on paper, trying to put it into place.

The final detail he added was the scales around Sirius’ hips, the way they gracefully blended with the jagged tattoos on the smooth skin of his stomach, which was well-toned from a lifetime of constant swimming. His focus was so intense that the paper nearly faded away, as if his brush was tracing over Sirius' actual skin and scales, the distance of art dissolving into something he wanted to be real. The intimacy of it made his hands shake, and he had to put down the brush for fear of ruining the whole.

After that, he knew he had to find Sirius. He had to talk to him, had to figure this out. He had to try to see if Sirius felt anything like what he did.

The sharks on the beach were still untouched. The lagoon was still empty. Remus didn’t let it stop him this time. He dropped Sirius’ doorbell-rock, and he didn’t let the lack of response to that stop him either. If his worst fears were true and Sirius had abandoned the lagoon, he might as well know it now.

He cast his swimming charms and dove straight down, heart pounding, turning to peer into Sirius’ cave.

At first he thought it was empty. The bioluminescent algae and skylight brought enough light in that no one should have been able to hide, and Remus saw only seaweed and shadows. He persisted, however, and as he swam inside, the shadows in the depths of the largest patch of seaweed formed themselves into the shape of Sirius, curled tightly around himself so that his tail and wide fluke covered all the rest of him. He was half-buried in the black sand and almost completely camouflaged.

The sight made Remus’ heart twist. How long had Sirius been like this? He hardly looked alive. Remus swam closer, looking at the base of Sirius’ fluke, relieved to see that the small veins there—the same ones he had just drawn from several different angles—were pulsing gently with life.

He had seen Sirius sleep underwater by now, with his arms and tail wrapped sweetly around the seaweed like a human would wrap up in a blanket. This was no sleep. It was just misery, and Remus couldn’t see it without feeling it as his own and needing to make it stop.

Sirius had to know he was here. Remus had learned, through unobtrusive observation, that while Sirius’ underwater senses were nowhere near as omniscient as he had claimed on that first day, he would have no problem tracking movement that was only a few meters away, as Remus was now. That meant he was being snubbed, but he didn’t care. He swam closer and reached out one hand to touch the side of Sirius’ tail in lieu of his torso, which was lost somewhere amongst the sand and seaweed. His face was tucked far under his fluke, also completely out of view.

He didn’t make contact before Sirius’ fins and fluke suddenly flared out wide all in unison. The sharp hunting spike at the base of his tail jerked upright, and Remus quickly withdrew his hand. It wasn’t body language he had seen Sirius display often, but he knew what it meant. It was a warning, a threat.

Remus curled his hands back into himself, horrified that he could provoke a response like that. He turned in the water, kicking away, chest aching, and returned to the surface. He pulled himself up onto Sirius’ sunning rock so that he would have the privacy of air, so Sirius wouldn’t be able to sense him as he wrapped his arms around himself, as the tears slipped down his face.

Everything was broken. Sirius was hurting, and he didn’t want Remus to comfort him. There didn’t seem to be anything he could do, and, as he discovered a moment later when he looked down through the clear water to the coral below, that wasn’t even the worst of it.

He dove back into the water and stared in horror at the coral near the entrance to Sirius’ cave, at the white, bare branches that reached upward like skeletal fingers. The white portion was nearly as large as Remus' body, a dozen times bigger than anything he had seen in the reef before.

The coral was bleaching. Sirius clearly hadn’t come out of his cave in days, and he had said the reef wouldn’t survive without the sharks. Remus had assumed that was an exaggeration, but it appeared to be true. Whether it was because of the disruption of the balance of predator and prey, or because Sirius hadn’t been singing to the coral, his fears were coming true.

The reef was dying.

This knowledge banished Remus’ self-pity and anxiety and replaced it with something much more powerful: determination. This wasn’t about Sirius hating him or about his fears of having to leave the island anymore. It was about something much more basic than that, the thing that lay underneath all of it. It was about the reef. He was not going to let the reef suffer for his mistakes, or for Sirius’ despair, or for any of it.

He burst from the water and got right to work, following the plan that formed in his mind as his feet ran across the sand, one urgent footstep at a time, one thing following another.

The reef needed Sirius. Sirius needed help. He didn’t want Remus, so Remus would bring someone he might accept help from. He would go get James.

+++

There wasn’t a boat on the island, and Remus had foolishly not had the forethought to bring a broom, but he wasn’t a wizard for nothing. It took only an hour or so of transfiguring with the pile of lumber and junk he had pulled out of the lighthouse shortly after arriving and he had a small but serviceable vessel. He levitated it down to the beach and splashed it into the water with intentional force, half-hoping Sirius would come to investigate this strange new presence in the lagoon. It didn’t work, but Remus was undeterred. He loaded the boat with the sharkskin, teeth, and a bit of the meat, thinking that James and Lily might be able to make use of it, and steered the little craft out into the open ocean, using his wand and an improvised charm as a makeshift propeller.

It must have made a racket by merfolk standards, because he was only about two-thirds of the way to James and Lily’s island when he spotted a flash of brown and red beneath the waves. James’ head popped up a moment later, smiling wide with surprise and welcome.

“Remus! What are you—“ He stopped cold, eyes wide, when he saw the pile of sharkskin and teeth in the back of the boat. His smile dropped away, and his face grew ashy. “What happened? Where’s Sirius?”

Remus explained as quickly and objectively as he could, and James’ face grew more grim with every moment.

“You did the right thing,” James said when Remus was done. “I’ll go to him right away. Tell Lily for me!”

He dove without another word, and Remus watched his red and gold tail disappear into the water with mixed relief and trepidation. He desperately wanted to follow, but he did as he was asked and continued on to deliver the supplies and the message to Lily.

Lily met him at the edge of the reef, beckoning Hari out of hiding once she saw who it was in the boat. She looked just as disturbed as James by the news, and Remus cursed himself for not doing this days ago. He should never have assumed Sirius’ fears were anything but justified.

Lily accepted the sharkskin and teeth with gratitude, but thankfully didn’t try to keep him. “You should be there,” she said firmly. “You’re part of this.”

That didn’t bode well, in Remus’ opinion, but he couldn’t argue. He turned his little boat around and made his way back to Sirius’ island.

He nearly cried with relief when he saw two figures below the surface in the lagoon, moving slowly over the reef. Whatever James had done or said, it had clearly been effective. He had probably gotten here less than an hour before Remus himself had, but he had already coaxed Sirius out of hiding, and Remus could hear a few weary notes of song as Sirius tended the coral. He was also relieved to see that the gory mess of the skinned sharks was now absent from the beach, perhaps dragged out into the open ocean for disposal.

Neither of the mermen even looked up as Remus’ boat went over them, however, and it seemed to be a sign. He desperately wanted to dive into the water, to check on both Sirius and the reef, but he could tell he was not welcome. So, he bundled up his feelings and pulled the boat onto the beach. He couldn’t make himself go up to the lighthouse, however. He sat on the sand in the afternoon heat instead, feeling the sun-warmed grains curling up over his feet, and hoped.

After a while, he saw the dark shape of Sirius shoot past under the water, headed straight for his cave again, and sighed. Thankfully, James was less avoidant. He emerged from the water a moment later, and pulled himself up onto the beach to sit next to Remus, his long tail trailing down to rest in the waves.

“Is he all right?” Remus asked, renewed anxiety making his whole body tense.

“Honestly, no.” James sighed. “But he will be again, at some point.”

“What about the reef? He said it wouldn’t survive without the sharks...is it really that bad?”

“The sharks are important,” James said slowly. “But his fears are more complicated than that.” He looked at Remus sidelong, dark eyes unusually serious. “Did he tell you about his childhood?”

“Not really. Just that he grew up in the shipping lanes.”

“Yeah, that’s what I thought.” James sighed again.

“What does that have to do with the reef?” Remus didn’t see the connection, but there must be one. It didn’t seem like James was simply changing the subject.

“He probably doesn’t want you to know. I think that’s why he likes you so much. You only see his competency. But it’s not the kind of thing that can stay a secret forever.” James was quiet for a while, seeming to watch the waves swirl around his fluke. Remus waited, a bit uncertain about being given one of Sirius' secrets without his consent, but his desire to know was so strong, it was impossible to deny. He wanted to know every piece of Sirius' thoughts and story, just like he already knew the shape and direction of every one of his scales, the pattern of every tattoo.

“Do you know what a critical period is?” James asked at last.

“Do you mean...like, in development?” Remus asked, grasping a little.

“Yes. Where there‘s an age where you're supposed to learn something, and if you don’t...well, you can't.” He lifted his tail out of the water for a moment, the fluke tense, and then let it slide back under. “We have a critical period with singing. It’s a parent’s responsibility to let their child hear many kinds of song while they're little, so they’ll have the experience to draw on when they’re older.”

Remus thought he could see where this was going, but he waited while James took a deep breath and let him continue.

“The—fuck, I can’t even call them parents—the _adults_ in Sirius' pod didn’t do that. It was neglect. Criminal neglect.” James' voice was clipped, his fins clasped tight to his tail under the water.

“But...Sirius can sing. I’ve heard him.” He didn’t do it as often as Lily had, but he did sing. “I’ve seen him sing to the coral, and...that’s how...the sharks...”

He trailed off. The way Sirius had killed the sharks had seemed different from what he did with the coral, but Remus didn’t see how it could be called anything but the merfolk version of singing. If anything, it had seemed much more fully-formed than the little, halting melodies Sirius gave to the reef.

James nodded sadly. “I taught him to sing to the coral, and it wasn’t easy. It took him almost a decade to learn even the little bits he can do and...well, I don’t hold it against him or anything—it’s actually a miracle he can do anything at all—but it’s not much. It’s nothing like what the rest of us take for granted. And, as for what he did to the sharks...that’s what happens when no one teaches a Mer what to do. That’s all we have that's innate, just that. I suppose you could call it a defense mechanism. The rest has to be learned.”

Remus nodded, understanding now why Sirius had always seemed to struggle with only a few seconds of singing to the coral, while Lily had been able to hum to her reef almost continuously, without even seeming to notice what she was doing.

“You have to understand,” James went on, “it‘s basically a disability, like being born blind, only it carries a lot more stigma. The coral-dwelling Mer think...they think not having song means you're violent, an animal. It’s just stupid prejudice, of course, but he‘s been fighting it since he came to us. Most of us don’t learn the ecology of coral reefs or any of that stuff. Fuck, I don’t even know what to call most of the fish in our reef. We just sing, and that’s all it takes. He had to read every marine biology textbook he could find for the council to even consider letting him take care of a reef, even a poky little one like this that no one else wanted to bother with. They come every month to evaluate the health of the reef, and they're bastards about it. If there‘s no sharks...”

“Surely they wouldn’t make him leave!” Remus cut in.

“They would. They _will_ ,” James said grimly. “It‘s not just that there aren’t any sharks. He-he _killed_ them. They're going to see it as confirmation of their bias against him. They’ll assume he can’t be trusted.”

“There must be something you can do!” Remus protested.

“I’m just one person on a council of nearly thirty. They won’t listen to me. They might assign the reef to someone else, but that will take months, and in the meantime, if they make him leave...” He sighed, face drawing down into lines of grief. “The truth is, all the reefs in this area would be bleached by now if it weren’t for us singing to them. If Sirius leaves, the reef probably will die. _That's_ what he means when he says the reef can’t survive without the sharks. It won’t survive without _him_ , and without the sharks, the council will think he's failed. They won’t let him stay.”

“That’s crazy! It can’t be better to just let the reef _die!”_ Remus protested, feeling his chest burn with the unfairness of it. “Besides, it was mostly my fault and—won’t more sharks come?”

“They will eventually, probably from my own reef, since it’s the closest.” James sighed. “But not in time. The council representatives come to inspect right after each full moon, and that’s only two days away.”

“I know.” Remus winced, glancing up at the afternoon sky. He could already feel a faint ache in his bones.

Hearing about all this made Remus feel even more frustrated and worried, but there was also a part of him that noticed something clicking into place in the back of his mind. He and Sirius shared something here. They were both judged for something that wasn’t their fault, something that they could easily render harmless if only given the tools and trust to do so.

Remus had long ago given up on hating himself for changing into a wolf each month. He had hit rock bottom on that years ago and realized he wouldn’t survive if he let himself live in such self-hatred. It wasn’t really the wolf that was the problem anyways. It was the humans that told him he was an animal, all the while denying him the things he needed to keep that from becoming a self-fulfilling prophecy. He just needed to give the wolf a safe, kind place, and no one had ever seemed to truly understand that. They had preferred to lock him up in a ministry cell that, while technically safe, would have been considered inhumane on any other day of the month. It was only natural that werewolves would try to avoid such brutal treatment by making do at home, without proper supervision or education, and that was how the disease spread.

Sirius’ disability was even less of a true threat to his people. It was abundantly clear that he could choose not to use his instinctual, deadly song, which all merfolk apparently possessed anyways. And he had more than made up for his inability to sing, as evidenced by the reef thrumming away peacefully in the lagoon.

“I have to talk to him,” he said at last. He felt, for the first time in his life, that he actually _wanted_ to tell someone that he was a werewolf, because now he had hope that Sirius would understand. And there was another reason too. “I think I can help. Do you really have sharks to spare at your reef?”

“Lots,” James said slowly. “But even I can’t sing well enough or long enough to get them to come all the way over here.”

“I think I can, in a manner of speaking.” Remus smiled. “Have you ever heard of the Imperius curse?”

+++

After confirming the details of the plan, James dove back into the water to convey it to Sirius. Less than a minute later, Remus saw Sirius’ dark-haired head hesitantly poke up above the surface near the sunning rock. Remus hurried over to talk to him, his core warming at the sight of the face he hadn’t seen in days. Sirius’ hair was twisted and held up with his hair sticks again, and his face—haggard and hollow after his self-imposed isolation—showed that he was waging a war between fear and hope.

“Can you really do it?” he asked, voice uncertain.

“Yes.” Remus climbed onto the sunning rock, leaning down as far as he dared. He was afraid of somehow doing something to drive Sirius away again.

“It will work, Sirius!” James swam over to join them, tucking his tail up against Sirius’ to talk. “It has to. I simply can’t stand it otherwise. I have to go back to Lily and Hari now though. Remus, I’ll see you tomorrow?”

“Yes, early,” Remus confirmed. He would have to experiment, but he was pretty sure he could only charm one shark into obedience at a time. That meant making multiple trips, and it would all have to be done quickly, before nightfall and the transformation came.

“I’ll round up some candidates for you,” James promised. He wrapped his arms around Sirius’ shoulders, hugging him tightly and clicking softly. Sirius responded in kind, and then James unwrapped his tail and swam away, out of the lagoon.

“It will work,” Remus repeated, seeing Sirius’ melancholy look.

Sirius just nodded, eyes downcast. “Thank you.”

There was a long moment of silence. Remus felt like he was bursting with things to say, but he still wasn’t sure what might scare Sirius back into his cave, and he didn’t think he could stand that.

Finally Sirius said, “James told you, didn’t he? About what’s wrong with me.”

“Yes. It’s not true though.”

That made Sirius look up at him, frowning. “Yes, it is. I can’t sing—”

“I’ve heard you sing to the coral,” Remus said calmly, just as he had to James.

Sirius’ face twisted. “That’s not anything. You haven’t been around us enough to know the difference, but you’ll probably hear James and Lily sing sooner or later. What I can do…It’s nothing. It’s pathetic.”

Remus felt his insides swell at that, and he couldn’t let himself hover over Sirius on the sunning rock anymore. He slid into the water and pressed both his legs together in imitation of a tail, then wrapped them around Sirius’ tail, the closest he could come to the conversational embrace the others used. It wasn’t nearly as much comfort as he wanted to offer, but it was something. Sirius returned the gesture automatically, as Remus had hoped he would.

“No, _that’s_ the part that isn’t true, Sirius,” he said, voice firm. “There’s nothing pathetic about what you’ve done with the reef here, and I’m sure part of you knows it. You’ve kept the coral alive. You kept _me_ alive. That isn’t pathetic. It’s amazing.”

Sirius’ breath left him in a shaky rush, and he straightened his tail suddenly, which pulled Remus down slightly in the water and closer. Remus found himself flush with Sirius’ chest with Sirius’ arms wrapped around him. Remus returned the embrace readily, and Sirius’ face rested on his shoulder. He was shaking all over.

“I don’t know what to do,” he whispered. “I’ve never sung in the reef before—not like that—and…” He took a shuddering breath, and it came out as a sob. “My fish are afraid of me now.”

“Oh, Sirius…” Remus held him as tightly as he could, feeling the weight of grief so heavily he was surprised Sirius’ slowly undulating fluke could support them at the surface so easily. Sirius' tears were hot on his shoulder. “They’ll learn to trust you again, with time. Won’t they?”

“I hope so,” Sirius said quietly against his skin. “I don’t know. It’s all my fault. I was careless with the dolphins, and then…I should have taken you back to James. He would have been able to control the sharks at his reef and heal you—“

“We were a lot closer to home,” Remus broke in. “You have no way of knowing what would have happened if we had tried to swim all that way. An open-water shark could have found us. I could have bled to death! You did the right thing.” He sighed. “I’m sorry it turned out the way it did, though.”

Sirius’ hands slid further around his back. “Also, I shouldn’t have taken it out on you. I’m sorry. I was just so…I’ve never done anything so monstrous.”

“It wasn’t monstrous!” Remus said fiercely. “You saved me. And, besides, I know something about monsters, and you definitely aren’t one.” He pulled back a little so Sirius could see his face, surprised by how much he wanted to linger, how much he wanted to stroke his hands down Sirius’ arms or trace the lines of his face. “I have something to tell you too. I’m not what you think I am, or not entirely. I’m a werewolf.”

Sirius pulled back a bit more, and they settled into the regular, half-seated position, arms floating freely from each other.

Sirius was searching Remus’ face, as if confused. Remus assumed he was trying to figure out why this had been kept a secret all these weeks, but then Sirius surprised him.

“I…I’m sorry, Remus, I can see that means something to you, but I don’t know what.”

Remus was momentarily speechless. He didn’t tell people what he was often, but when he did they always reacted with shock, dismay, or fear. Never, in all of his years, had he met with someone who simply had no idea what he was talking about. The idea made laughter bubble up in him, a relief when he was used to so much worse. Quickly, he explained, cherishing the complete absence of fear or disgust on Sirius’ face as he did so.

“I won’t be a danger to you, but I assure you, other humans do consider me a monster. That’s why I came here. I wanted to be away from that.”

Sirius nodded, brows drawn together in encouragingly empathetic shared frustration. “Then they’re assholes, and you _should_ want to be away from them. No one here will care. _I_ don’t care.”

“I know,” Remus said, smiling. He wrapped his legs around Sirius a little tighter, feeling more grounded than he ever had before, for all that he was meters above the seafloor.

“James and Lily taught you to fin up,” Sirius observed, one side of his face lifting up into a small smile. It was the closest to normal he had looked since they had swum with the dolphins, days ago.

“Yes, as well as I can with my ridiculous, land-lumbering limbs,” Remus said, teasing gently, and loving how it made Sirius’ smile widen. He craved more of it. “Speaking of which, will you come out of the water for a bit? There’s something I’ve been wanting to do with you.”

Sirius raised his eyebrows and seemed on the verge of making a lewd comment. He refrained, however, which Remus appreciated. He was only just beginning to understand what he wanted from Sirius, and he didn’t want to be rushed.

Remus pulled himself out of the water and asked Sirius to wait, then went up to the house to get a few items. He picked up a few more things on the way back and returned with a full basket to find Sirius on the sunning rock, right where he should be. Even better, he slid over a bit to make room for Remus to join him.

Remus did so gladly, loving the warmth of the stone and of Sirius' body next to him. Sirius was already craning his head around to see the basket, as eager as a child about to be given a present.

“What is it?”

“Well, I know making fun of humans is your favorite hobby, so I thought this might cheer you up.”

Remus opened up the basket and brought out a few basic picnic supplies, including a small tin, which he gave directly to Sirius. He and Sirius had been living in close proximity for nearly a month now, but they had yet to share a meal. Also, he had a feeling Sirius hadn’t eaten anything for days.

Sirius accepted the can with a smile and then burst into laughter when he saw the label. “Fuck, you weren’t kidding! You really _do_ eat fish from a can. 'Chicken of the sea,'” he read aloud. “What's chicken?”

Remus laughed. “How is it that you know the taxonomy, life cycle, and environmental needs of every species in your lagoon and yet you don’t know what a chicken is?”

“Oh, I see, it’s some kind of _land_ animal,” Sirius said with a purposely overdone air of aloofness. “My knowledge is far too specialized and useful for me to bother with _those_.”

“Obviously. Well, a chicken is a small bird that humans all over the world eat and most people agree is delicious.” Remus smiled wryly and tapped the tin of fish with his wand to open it. “It’s the tuna of the land.”

Sirius watched with a wary expression while Remus removed the lid from the tin. “I can’t believe I’m about to do this. It smells disgusting, you do know that, right?”

Remus leaned back on his hands, eyebrows raised. “I eat it all the time, you know.”

“You poor thing.” Sirius made a face as he scooped out a few flakes of light pink fish with his fingers. “Suddenly the human usage of silverware makes sense. No one could enjoy touching this with their fingers. And now you expect me to touch it with my _mouth?”_

Remus grinned. “Have you ever heard the expression, ‘chickening out’?”

“I have, actually.” Sirius winced but raised the tuna up to his mouth and took a bite. Immediately, his expression transformed from demonstrative, overdramatic wariness into authentic, unfeigned dismay. Remus couldn’t help bursting into laughter as Sirius coughed, eyes wide, hand over his mouth, and struggled to swallow. It was the closest to unlovely that he had been since Remus had arrived on the island. Even his fins reacted, jerking abruptly into a flared position, throwing up a little spray from where his tail still draped into the water.

“That—“ Sirius spluttered, turning the can, examining the text with a horrified, perplexed expression. “That is not tuna! It can’t be!”

“Well, it _is_ cooked.” Remus took the tin, tactfully replacing the lid and setting it far away, where the smell wouldn’t continue to offend.

“I’ve had cooked fish before, and it was fine,” Sirius said with strong disapproval. “ _That_ is not fine. That is a travesty. No wonder humans don’t care about ruining the ocean, if that’s what they think comes out of it. Have you ever had tuna— _real,_ fresh tuna, I mean? Do humans eat raw fish?”

“Yes. It’s considered a delicacy, actually.”

“Anything would be considered a delicacy compared to that.” Sirius shook himself a little, as if to banish the newly acquired sense memory. “As soon as I can drag James away from Lily and Hari for a day, we are going to catch you a tuna.”

“You can’t on your own?”

“Those suckers are fast, Remus.”

This, conveniently, answered a question Remus knew it wouldn’t be polite to ask: if Sirius or other merfolk ever used the fatal version of their song for hunting. He had no doubt it would be able to kill all the tuna within range, but clearly, Sirius didn’t even consider it as an option.

He watched the muscles in Sirius’ back move as Sirius folded himself in half to reach the water below the sunning stone, rinsing off the fingers that had touched the tuna and carrying a handful of water back up to his mouth. That was new too, although if Remus had thought about it for a moment he would have realized it was a biological necessity for merfolk to be able to drink salt water.

Sirius straightened back up, smiling. “Strangely, I actually do feel better, even if it does taste like something died in my mouth. Thank you for that…experience.”

“Do you eat fruit?” Remus offered him an apple from the orchard by way of apology.

“Sometimes. James and Lily have some trees near the shore.” He accepted the apple and took a bite gratefully. “I’ve had this kind before, I think. From a very friendly cargo ship captain.”

Remus nodded, assuming that whatever fruit James and Lily had, it was probably tropical, like everything else here. He ate an apple himself and then offered Sirius an apricot.

“Careful, it has a stone,” he said, a bit too late, as Sirius had clearly just encountered the pit with his teeth. Sirius didn’t seem to mind, however. His eyes were wide with delight.

“Oh, I like this one! How many did you bring? I’m surprised they’re still fresh. Did you use magic?”

“No,” Remus said slowly, a little confused. “Most fruit can stay fresh for a few days at least, and I only just picked it on my way down.”

Sirius’ eyes widened further. “This came from _here?_ ”

Remus nodded. Whatever European or American wizard had been tending the lighthouse in the past had set up an extensive network of charms to get the cold-weather fruit to grow here. He explained this to Sirius, who was craning his neck to look up the path towards the more elevated part of the island. The orchard was just out of view.

“Well then.” Sirius tossed the pit into the shrubs at the edge of the beach and leaned back on his hands, hoisting his tail out of the water. He gave it a little shake, and Remus was absentmindedly watching the drops of water fly from the fluke when suddenly the tail disappeared and he was looking at feet. Feet that were attached to legs that were attached to Sirius’ body.

Remus’ mouth fell open and stayed that way. He was half-convinced he must be imagining things, but the legs definitely looked real. They were light brown and devoid of hair, like the rest of Sirius’ skin and they were, like everything about Sirius, absurdly perfectly shaped, from the narrow ankles all the way up to the soft-yet-muscular thighs. Remus also couldn’t help but notice, with an attitude that was mostly but not entirely scientific, the distinctly human-shaped genitalia that had been added as well. Even with this undeniable detail, it seemed impossible. There was simply no way—

“Surprised?” Sirius said, his voice round with smugness. He lifted one leg, clearly not minding being stared at in the least. “It really is fun, how little you know about us.”

“But—you—“ Remus spluttered, still shocked beyond words. “I’ve been here a _month_ and you never—you never even said!”

“There was never a reason to. How many times do I have to tell you? Land is boring.” Sirius steadied himself with his hands and slowly pushed himself up to stand, treating Remus to a view of the perfectly curved dorsal side of this new, leggy body. This was probably an intentional display on his part, but Remus was paying more attention to the significant amount of wobbling in Sirius’ posture.

“Fuck, gravity is terrible,” Sirius mumbled. He took a few careful steps and then seemed to find his balance. He started walking with theoretical confidence up the beach, towards the path to the orchard. The effect was not quite convincing considering how slow he was going, but he didn’t look in immediate danger of falling anymore. “Are you coming? If staring is your goal, you’ll have to, or I’ll be out of sight!”

Remus finally collected himself enough to follow. He emptied the rest of the picnic supplies onto the sunning stone and brought the basket along. If they were going to collect fruit, they might as well do it properly.

“Do you want some clothes, or at least shoes?” he offered. He was watching Sirius' feet sinking into the sand, the coarse black grains sneaking up his legs further with each step, clinging to his bare calves. His legs, unlike his arms and torso, were not tattooed. They looked blank, out of place.

Sirius looked at him like Remus had suggested he grow an additional pair of legs to replace his arms.

“Absolutely not,” he said scornfully. “I’m not a _human_ , no matter what limbs I have at the moment.” He held up his hands, flexing the fingers to put the distinctly inhuman webbing on display.

Remus raised his eyebrows doubtfully, and refrained from making a comment when Sirius reached the path and his steps slowed further still as his bare feet winced over the rough pebbles and lava rock. Remus had spent a month working his feet up to be able to handle the island’s terrain barefoot. Sirius’ soles were clearly not well suited for the challenge, but it wasn’t far, and Remus doubted his shoes would fit Sirius anyways. His feet seemed to be a few sizes larger, proportional to his taller body.

Sirius looked down as Remus fell into step beside him, clearly thinking the same thing. One side of his mouth quirked up. “I’m still longer than you.”

“Taller,” Remus corrected absentmindedly. It was technically true, but it was a bit hard to conceptualize. Actually, Sirius seemed bizarrely small like this. His legs were nearly three feet shorter than his extravagant tail and fluke.

“I can’t believe you’ve never heard that Mer can wear legs,” Sirius said. “Don’t humans have stories about it?”

“Yes, but I assumed they weren’t true, since you never let on.”

“But surely you know about how the females come up onto land and seduce human men. It’s the only way we can reproduce.”

Remus frowned. That didn’t seem consistent with the fact of Hari's existence. The child seemed clearly a product of James and Lily. But perhaps some mermaids made an effort to find humans that resembled their merfolk mates?

“That’s…unexpected,” he said, trying to be polite. “But why are there male merfolk then?”

“Decoration,” Sirius said smoothly. “And then, after the mermaid mates with the human, she devours him.”

Remus sucked in his breath, actually convinced for half a second, but then Sirius started laughing. Remus groaned. “Nothing you just said is true, is it?”

“Of course not!” Sirius said, and Remus rolled his eyes, although secretly he was glad to see Sirius in such a good mood, considering everything that had happened. “Except that we are quite decorative.”

They reached the orchard a few minutes later, and Remus pointed out which tree had the apricots. Sirius looked up at the tree canopy, clearly intimidated.

“How do you get them down?”

“I’m very tempted to tell you you’ll have to climb, but I think that would be risking broken bones,” Remus said wryly. Sirius still didn’t seem to have completely mastered verticality. Tree climbing was clearly beyond his ability. “At the very least, you would get all scraped up. Human clothing does have a certain functionality to it.”

Instead, Remus raised his wand, aiming carefully for the fruit that looked the ripest, and cast a few summoning charms.

“Just so you know, I could actually have done that from the beach,” he added. “So your transformation wasn't really necessary.”

Sirius eagerly accepted one of the fruits and took a large bite, face going slack with eye-fluttery delight. Remus watched for a moment and then let his gaze travel downwards, wondering where the transition truly began. The upper half of Sirius’ hips looked nearly the same as usual, so presumably his pelvis was the same in both forms. Did he have human-shaped femurs in his normal form? Remus pictured the shape of the tail in that area, trying to use the curves of the muscles to extrapolate the shapes of the bones within.

“I wouldn’t call it a complete waste, though,” Sirius said with a smug smile. “After all, checking me out seems to be _your_ favorite hobby,” he added, repeating Remus’ words from earlier. At the same time, he leaned in to pull another apricot from Remus’ basket.

Remus felt his proximity as a wave of pressure and energy along that side of his body, as heat in his face. He wondered, with that analytical part of himself that seemed to get harder and harder to focus on the closer Sirius got, if this was how it felt to Sirius to sense the movement of other creatures in the water. Remus was sure that he would have been able to close his eyes and reach out to touch any part of Sirius' body with complete accuracy. He didn’t close his eyes, though, and he didn’t move away either, not even caring about being teased for being caught looking, once again.

Sirius didn’t move back either, instead holding the apricot in one hand, looking Remus over. The sun was setting, lending warmth to his usually cool silver gaze, and gilding the orchard in amber tones.

“So,” Sirius said at last. “Are you sexually attracted to me yet?”

The boldness of this made Remus jerk back instinctively. He didn’t even stop to evaluate the question, too caught off guard by what he hadn’t consciously realized was Sirius coming on to him. “Why do you keep doing this? I told you, I don’t experience sexual attraction outside the context of—“

“Romantic relationships,” Sirius finished curtly, taking a full two steps backwards. “Demisexual. I didn’t _forget._ I just thought—” He didn’t finish, and his face closed off abruptly, like a door slamming shut. “What is it with you humans and your labels and boxes anyways? You put them everywhere! Around your sexuality and your gender and your countries...you even put lines through the _ocean_ , which is completely ludicrous. It’s all one thing!”

Remus stared, utterly shocked at this abrupt shift. “Are you—you can’t possibly be equating geopolitical territories and identity labels. They aren’t even remotely the same thing!”

“Are you sure?” Sirius put his hands on his bare hips. “It’s only because you’re so repressed and fixated on your differences that you have to use those words or divide up your countries at all. You wouldn’t need words like ‘homosexual’ if you didn’t have homophobia.”

“That’s not how it works, not at all,” Remus said, starting to feel angry. He didn’t blame Sirius for resenting humans for trying to claim the oceans—which they clearly had no right to, in comparison to the Mer—or for pollution or climate change. But this was something else. “You have no idea what you’re talking about. Identity labels, when self-determined, help us understand each other and ourselves. You can’t understand differences if you can’t identify what they are! And I’m not _repressed_ , I’m—“

“Demisexual, I know,” Sirius finished again. The steam seemed to have gone out of him in the face of Remus’ irritation, however. “Sorry. I don’t think you’re repressed. I’m sorry.”

He sat down suddenly on the ground, as if the experience of standing up on legs was suddenly too much. Whatever playfulness he had regained over the course of the afternoon was suddenly gone, replaced by the stress and fear that had been weighing on him for days.

“I’m sorry,” he said again. “I tried to pass for human once, back before I found James’ pod, when I didn’t have anywhere else to go. It didn’t go well.”

Remus thought about Sirius’ easy flirtatiousness, which he clearly didn’t see a barrier to expressing with other males, and understood. He sighed and sat down next to Sirius, feeling mollified now that he recognized that Sirius’ little rant hadn’t really been about him. He readied himself to listen to whatever firsthand experience of homophobia Sirius was about to relate, but it seemed Sirius' mind was back on the reef.

“What if it doesn’t work?” he asked, voice low. He swallowed, looking down at the apricot in his hand. “I believe you when you say you can bring the sharks, but the council representatives might be able to tell the sharks are new here. They might notice the fish are afraid of me.” He closed his eyes, clearly overcome with the painful thought. “They might still make me leave. They can’t make _you_ leave, though. You can stay here, and I’ll go to James’ reef. It’s not far, but it’s not here.”

He looked back up at Remus then. He seemed to have dimmed down to some lower level, as if he were diminishing along with the light as the sun set.

The thought of Sirius leaving was devastating, even if he would only be a short visit away. He was a part of this place, a part of the reef. It didn’t matter that he had used to live out in the open ocean. Like the triphasic life cycle of the barnacles Remus had originally come here to study, _this_ was the part of Sirius' life that mattered, the part where he found a home and clung to it with everything he had. He belonged here, with the reef. Remus felt it in his bones.

“Then you're just going to have to convince them,” Remus insisted. “Tell them it’s my fault and you’ve forbidden me from ever going in the water again. Tell them whatever you want. But if they do make you leave...” He reached out and took Sirius’ hand, feeling the warmth, letting his fingers slide against Sirius’ skin, just a little. The webbing between his fingers was soft and smooth, cooler than the rest of his hand. Sirius watched him intently, brows drawn together with worry and hope. Remus did his best to soothe the worry and answer the hope. “If they make you leave, I’ll take care of the reef for you. There must be spells I can use to help the coral, and if there aren’t, I’ll invent some. I don’t know if I can do a good enough job, but I’ll try.”

Sirius’ eyes were wide, as if this was not actually what he had been hoping for after all, but was somehow even better. He abruptly let go of the fruit, letting it roll away on the ground, and held Remus’ hand in both of his.

“Thank you.” For a moment it seemed like he might say something else, but perhaps he was too overcome with emotion, because he simply repeated, “Thank you, Remus.”

“I love the reef too. I don’t want it to die either,” Remus said gently, and it was true. He wouldn’t be doing it for Sirius, not really. The reef itself was reason enough. “Speaking of which, I should go.”

He pulled on his hand, and after a second, Sirius reluctantly let go.

“Now? But—“ Sirius scrambled to pick up the apricot, adding it to Remus’ basket. “We didn’t eat them all yet. And your things are still on the beach…”

He seemed oddly breathless, and it made Remus wonder if there were consequences for being in this legged form too long. He thought it was unlikely, though, or Sirius would never have attempted to pass as a human in the past.

“The fruit will keep,” Remus reassured him. “Take it with you if you like. I need to leave at first light tomorrow if I’m going to have time to bring back enough sharks to reassure the council, and…it’s better I do it earlier in the day. The afternoon and evening before the transformation are hard, sometimes.”

That was a bit of an understatement. He usually spent the entire day before the full moon in bed, his body sore from the oncoming change. He could already feel it. The moon had just risen, and his joints were starting to burn, even if it wasn’t yet full. He wasn’t going to let that stop him from doing whatever he could tomorrow, though.

“All right.” Sirius stood up carefully and took the basket of fruit. “Let me know if there’s anything I can do. Please.”

Remus nodded, but he didn’t offer any suggestions, since there truly wasn’t anything Sirius could do about the transformation. He just said goodbye and made his slow way back to the lighthouse and an early bed.

+++

The next day went largely as planned. Remus tried, but he could not reliably control more than one shark at a time with the Imperious curse, so he had to make trips. It was nearly an hour each direction, so almost all of his day was spent in the boat, going to and fro, tailing a reef shark on each return journey.

James and Lily did what they could by herding the sharks chosen to make the journey into position, using their voices which joined together in a haunting, full-bodied duet. Hearing it made it clear to Remus that, objectively, what Sirius and James had told him was true. Sirius could not sing anything like that, except when using the deadly defense mechanism. It only confirmed the other half of Remus’ belief, however, that every note Sirius did manage was far more valuable for being so hard-won, and it fueled Remus' determination to do whatever he could to keep Sirius with his reef, where he could make a difference.

He needed that determination, as it turned out. The moon was already carving away at his energy and concentration, bringing more pain with every passing hour. By the fourth trip, he couldn’t hide it from James and Lily any longer, and he told them what he was. They reacted in much the same way Sirius had, and Remus felt another weight lifted off his shoulders, although those shoulders persisted in aching.

When he returned for the sixth shark—the last one he would have time for—he was weak and hazy from pain. James took one look at him and said, “Get in the water. I’ll sing for you. It will help.”

Remus didn’t need further encouragement, although it felt oddly disloyal to Sirius to let someone else sing to him, in the way that Sirius would probably never be able to do. He didn’t want to waste energy on his underwater charms, so he held his breath, squinting through the blur as James swirled around him, singing with such clarity and fullness that it seemed as though every water molecule in Remus' body wanted to sing along. In the span of a few seconds, all of his muscles relaxed, the pain washing away like footprints in sand when the tide rose to cover them. His lungs relaxed too, and he sighed out his air, utterly unconcerned. James swam over a moment later and pulled him to the surface, wrapping his tail around Remus' legs for stability—finning up, as Sirius had called it.

“Better?” he asked and smiled when Remus nodded. “Good. You'd better head back then. It won’t last long.”

He offered a foothold while Remus hauled himself up into the boat again, and hung on the side for a moment. “This is going to be a good place for you, Remus the werewolf-human. I’m glad you're in our pod.”

He flipped away before Remus could express his shock at being so included, and Remus was left to mull it over on the way back home instead. He couldn’t remember the last time he had known someone like James or Sirius, someone who was so unburdened by fear and judgment that they were actually willing to help. Lily and Hari were already a blessing in his life as well. On his first trip back, Lily had given him a wand holster, which he now had strapped to his arm, made from the sharkskin he and Sirius had salvaged. He would never have to be without his wand when he swam again. Hari seemed to take the giving of the gift as a sign that Remus could be trusted, because the baby darted out from their mother’s embrace for one quick swirl around Remus’ torso before swimming back to hide in her hair with a shy smile.

Sirius was lucky to have found such an accepting family, too. It seemed his disability was enough to make him a pariah amongst the coral-dwelling Mer, yet Lily and James clearly didn’t share that prejudice in the slightest.

They were both lucky, and Remus couldn’t feel anything but honored to be considered part of their group. He wondered if it was only James that thought of him that way, or if it was a sentiment Sirius shared. He knew which one he hoped for.

Sirius swam out to meet him when he returned but didn’t surface, instead trilling nonstop to the shark, welcoming it. He had spent the day at his home reef, talking to both the familiar fish and the new arrivals, trying to regain their trust enough that the council representatives wouldn’t notice the rupture in good relations.

Remus sighed as he released the final shark from his magical grasp, and it darted away to swim with its companions on the edge of the reef. He watched from the boat for a moment while Sirius communed with them, mostly by talking, but occasionally with little snatches of half-voiced, halting song. He was too tired to linger long, however, and guided his boat into the lagoon and above the tide line.

He was about to trudge up to the house to wait out the last uncomfortable hour until the moon rose when he heard the now-familiar sound of Sirius surfacing near the sunning rock, a little splash and a quick breath as Sirius realigned himself internally to breathe in open air.

“Remus, wait.” He sounded hoarse from exhaustion, and Remus was sorry to see that his appearance matched the sound. His face was drawn and drained, and he raised himself only a few inches above the surface with a shaky grip on the rock, as if the challenge of gravity was too much for him. He had probably been singing more than was sustainable, and it hurt Remus to see it, even though he had, objectively, been doing the same thing to himself.

“You should rest,” Remus said. “Whatever you’ve done, I’m sure it will be enough. You look terrible.”

Sirius laughed tiredly. “That’s a first. And here I thought your aesthetic attraction to me could weather all storms.” He paused, swallowing, and then lifted himself out of the water, clearly not without effort. His hair was done up in two french braids, which he had pinned to the back of his head with his bone sticks, presumably so he didn’t have to worry about it while he worked. “Come here? I need to talk to you.”

Remus relented, coming over to sit on the sunning stone. The sun was at a low angle now, but the stone was still warm. It felt soothing on his tired legs, as did moving closer to Sirius, as if Sirius himself possessed the same kind of comforting heat. It drew him in, and Remus let it happen, too tired to analyze what exactly it meant other than that he would happily have pressed his entire body up against Sirius’.

Sirius looked down at where they were touching, the upper part of his tail against Remus’ thigh. His mouth twisted with an emotion Remus couldn’t identify, and the lower part of Sirius’ tail rose out the water to follow the line of Remus’ bent legs, the fluke coming to rest on the stone past his feet. Sirius’ shoulder moved closer too, until their skin was just barely touching. Remus felt another wave of exhaustion roll over him as his body tried to respond to the safety of the contact by dropping into sleep, tried to lure his head down onto Sirius’ shoulder. But Sirius’ arm was tense against his own, and it reminded Remus of why he had been called over.

“What did you want to tell me?” he asked, stifling a yawn. It was odd to experience the onset of the transformation with the pain dulled by James’ song, although he thought he could feel the effects wearing off. His head already ached more than it had a few minutes ago.

“I’m sorry,” Sirius said, very quietly. “When…when the sharks died, I was so messed up about it…”

“You already apologized for that,” Remus said, tilting his head up to frown at him. “It’s fine, Sirius.”

“I did, but I’m realizing I need to be more specific. About several things.” Sirius was looking out over the reef, his chin tilted in a way that seemed unusually vulnerable, his voice pitched low. “I’m sorry for saying that you throw things out of balance, because it isn’t true. You do bring balance to the reef…because you bring balance to _me_. I like having you here. I love sharing the reef with you.”

“Oh.” Remus felt warmth rising up through his whole body then, pushing back the rising pain, a war between two fierce tides. He found Sirius’ hand where it lay between them and put his own over it. “I love that too.”

Sirius’ hand twitched under his, and he took a deep, shaky breath. “And I’m sorry about what I said yesterday too, because the truth is I don’t think your human lines and boxes are stupid at all. I’m just worried that I won’t fit into them, and that terrifies me because—because I’m falling in love with you.”

Remus’ breath caught in his throat, because somehow he hadn’t seen that coming. Also, Sirius was looking down at him now, face terrified but utterly sincere, and then suddenly he was leaning down, and their lips were touching, and Remus hadn’t seen that coming either.

It was probably the most gentle kiss he had ever received. Sirius’ lips were soft and patient, only asking, not taking. And Remus felt…nothing.

He felt _nothing._ Nothing but the throbbing pain in his head, the rapidly worsening ache in his joints, the twist of his guts getting ready to rearrange themselves, just like everything else. The kiss didn’t feel good—it didn’t feel like anything, and he _wanted_ it to. But it was just…nothing.

He jerked back, face hot, body curling in on itself and away from the warmth of Sirius’ touch, away from his mouth, his shoulder, his tail. 

“Oh fuck,” Sirius breathed, voice tight with concern. “I’m so sorry. I should have asked before I did that—Remus, I’m so sorry—“

“It-it’s all right,” Remus said shakily, but it wasn’t, even if it wasn’t Sirius’ fault. Right on the heels of the nothing was an entirely different kind of pain from the physical, a frustrated, wailing despair, because he _wanted_ this. Even in the midst of all the horrific nothing still pouring back and forth between his lungs, he was so sure of what he felt for Sirius…but when put to the test, his horrible, wretched body had betrayed him. Maybe he didn’t know himself as well as he thought he did. Maybe he _didn’t_ know what he wanted, what he was capable of wanting.

These thoughts swirled around in his head, panicked and mean in a way he seldom experienced lately, only when the stars of his life were truly misaligned…or when the full moon was looming below the horizon.

“It’s not your fault,” he managed to say at last. Sirius was hovering near but not over him, clearly overcome with guilt. “I—the full moon is so close. Everything hurts. I can’t—I can’t even think. I can’t talk about it, please.”

“It’s fine, Remus, it’s fine,” Sirius said quickly, voice distressed. “You-you don’t have to talk. It’s all right.”

“I need to go.” Remus’ mind was suddenly full of nothing but the transformation. The sun was right above the water. It was _setting_ and he was just sitting here, having an emotional breakdown. He pulled himself to his feet and started to retreat. “I have to get ready. It’s almost moonrise.”

The thought made him convulse with dread. The small part of him that was still rational tried to reassure himself that it would be different this time. There would be no cell, no chains, no disgusted stares from Ministry staff as he limped dizzily home the next morning. It was just him, and the island, and the reef, and Sirius.

Sirius was getting smaller as Remus stumbled backwards across the beach, his worried face getting less and less distinct. It was hard, even now, to walk away from him.

“You should probably stay in the water,” Remus said hoarsely.

“All right.” Sirius looked reluctantly between Remus and the water as if he had half a mind to transform his tail into legs and walk Remus up to the lighthouse. “I’ll be here in the morning, Remus. Be careful.”

Remus stumbled a bit as he turned, hardly even able to process such unfamiliar words, and ran, the pounding of his feet on the path like the rhythm of a drum foreshadowing the coming change. It didn’t take long. It found him, as it always did, and he crumpled, screaming, into the bloody embrace of the transformation.


	5. Mermen

Remus never felt fully cognizant while he was a wolf, so the next time he was aware of being part of the world was the next morning. The light pushed against his closed eyelids, and when he blinked them open, it was, for the first time, not to the bright lights and stone ceiling of a Ministry cell, but to blue sky. A moment later, his view was entirely of Sirius' miserable, worried face.

“You’re awake!” Sirius was scrubbing tears off his cheeks. His hair was a mess, halfway fallen out of the braided style it had been held up in the day before. “You fucker—you didn’t tell me it would _hurt_.”

As if summoned by that last word, the rest of Remus' senses began to operate. It _did_ hurt. He could feel where his hands and feet had been rubbed raw on the rough lava rock of the island, but much worse was the pain in his leg, a throbbing, pervasive pain that seemed to ebb and flow, as if pulled by a tide.

He was halfway in the water, he realized, and the waves were indeed pulling on the injury. He grimaced and tried to curl away, but the pain was shocking. He also made the mistake of putting his scraped hands into the sand to support himself.

“Your hands are bleeding,” Sirius said quickly, “and I think your leg is broken. The wrist part.”

“Ankle,” Remus muttered, collapsing back onto the ground and trying to brush off some of the sand from his palms without removing any more skin.

“I tried to heal it.” Sirius' voice was low and wretched with shame. “I can't. I’m so terrible at healing.”

“It's all right. I can do it.” Remus tried to sit up again and was overcome by another wave of pain, even though he had done his best to keep his ankle immobilized.

He was exhausted. He had practiced as many healing charms as he could get his hands on before deciding to tackle the transformations without the support of the unpleasant but still technically skilled Ministry healers. But he hadn’t counted on how the pain would blur his mind, and the charm for healing broken bones was a complex one. “I have to rest first, though, or I’ll fuck it up. I have to-have to sleep.”

Even as he said it, he felt a wave of despair. He would never be able to sleep while in this much pain.

“I can do that,” Sirius said. “It won’t take much. You must be exhausted.”

Remus nodded wearily, although he didn’t understand how Sirius could help. A moment later, though, Sirius had gotten a grip on his underarms and was dragging him around, pointing his head towards the water. He was obviously trying to be gentle, but Remus still cried out, desperately trying to stabilize his ankle through the movement. Then his head was in the water, just enough to cover his ears.

Remus winced, expecting the low, sand-filled surf to sweep over him a moment later, but there were no waves. He opened his eyes to see the protective wall of Sirius' tail curled around him, forming a buffer against the waves.

Sirius bit his lip, face drawn with concentration for a moment. Then he leaned down, bringing his head close to Remus' ear under the water.

It was just a few notes of song, feeble and weary, but somehow that was exactly what it needed to be. The fatigue in it found the same feeling in Remus' body and gave it more volume, until the tidal wave of his exhaustion was large enough to flood the pain entirely, and he slipped down into sleep.

+++

It was hard to tell how long he slept like that, dreamless and floating. When he woke at last, he was in his own bed in the lighthouse. A quick survey showed him that his hands and feet had been cleaned and bandaged, and his leg splinted. He didn’t remember doing it, and it took him a foggy minute to realize that meant Sirius must have done it. Sirius must have carried him up here as well, which couldn’t have been easy, considering his antagonistic relationship with legs.

Remus was still naked, but Sirius had thoughtfully strapped his wand to his arm so he would have no trouble finding it when he woke up. Remus pulled it out of the sharkskin holster Lily had made, took a deep breath, and attempted the bone-healing charm. To his relief, it worked, and he spent a moment taking in the odd, tingling sensation as whatever had been broken in his ankle healed itself. He healed his hands and feet with a quick charm as well, removed the bandages, and then rolled over to look at the rest of the room.

Sirius wasn’t here. Remus wondered how much time had passed. Had the council representatives already come and gone? He probably shouldn’t go down to the lagoon while they were here. He wasn’t sure how the typical Mer felt about humans, but he had a feeling it would be something along the lines of how chicken farmers felt about foxes.

He definitely felt better than he ever had while transforming at the Ministry. The scraped paws and broken ankle were unfortunate, but they weren’t an unusual consequence of the full moon. Overall, he was far less sore and miserable than he had ever been before. Now that he had successfully healed himself, he felt only relief and vindication. He had been right: his wolf form just needed more space and a bit of respect.

He lay on his back for a minute, appreciating the unusual feeling of being rested and comfortable. He let his eyes wander to the drawings and paintings of the reef he had hung up around his room, studies of the seaweed, coral, crustaceans, and fish. There was also one of Sirius, smiling in the midst of a school of welcoming, swirling fish. It was right above his bed. Sirius must have seen it.

The rest of his drawings of Sirius were still on his desk, and Remus could see, even from here, that they had been rearranged. Sirius had been looking at those too.

Remus wondered what he had thought of them, both the drawings of the reef and the paintings of Sirius himself. Did the art say the same thing to Sirius that it had said to Remus? Did it say _you belong here?_ Did it say _this is love?_

Sirius had done more than bandage him and look at the art. He had put food and water on the bedside table as well. The water was in a bowl, but the sentiment was there. Remus was surprised Sirius had known about the cistern that stored fresh water at all. The food was mostly fruit, perhaps a sign of Sirius' distrust for the canned fish and other packaged provisions Remus had brought with him. The sight of the apricots made Remus smile.

He was in the process of leaning over to reach for one when he noticed an unusual smell on his pillow, the smell of the ocean. It shouldn’t have been unusual at all, as nowadays he went to bed with salt in his hair more often than not, but this wasn’t just any oceanic smell. It was _Sirius’_ scent.

Remus leaned back and looked at his pillow, at the _two_ indentations there, the fine dusting of black sand, the single strand of long, night-black hair. Sirius had lain here. He had been right here while Remus was sleeping, perhaps wrapped around him closely in the way that Mer seemed to do platonically but a human never would with a mere friend. Sirius had been right here, and he had certainly been naked at the time.

Suddenly the inclination to eat was secondary to another urge, one which Remus welcomed with every bone in his body. The tingling warmth low in his belly was a relief, a blessing, and he was grateful that he was already unclothed, that there was no need to delay as he slid his hand down to touch himself.

It didn’t take long. Remus was no stranger to his own right hand, but this was different. Sirius' scent was in his nose, his image on the wall, his presence in every item in the house that had been moved or observed. He was surrounded by Sirius like the island was surrounded by water. He came with a quiet, grateful gasp, his face pressed into the pillow, mere moments later.

Afterwards, he relaxed into the tingling bliss, breathing deeply, feeling overwhelmed and so happy he thought he might start floating. He hadn’t been wrong about this either, despite last night’s false start.

Even better, apparently his feelings were reciprocated. Now that the full moon was no longer looming over him, he could look back on what Sirius had said the previous day and marvel at the miracle of it. Sirius loved sharing the reef with him. Sirius had kissed him. Sirius was in love with him.

After a few more peaceful moments, Remus sat up, put on his swim trunks—he was starting to accept there wasn’t much point in other clothing—and ate the food Sirius had left. Each mouthful of fruit tasted like a gift, left here by Sirius even when he had surely been exhausted, even when he had just seen Remus at his most monstrous. The thought made him eat quickly, and it wasn’t long before he was down at the beach.

He approached cautiously, but there was no sign of merfolk in the lagoon. It was already afternoon. They had probably come and gone. He didn’t see Sirius either, so he went over to drop the doorbell-rock into the water.

The rock hadn’t even touched the ocean floor below before Sirius came shooting out of his cave, tail whipping along through the water behind him. He burst through the surface right in front of Remus’ face, splashing him a bit, but for once Remus didn’t mind.

“Remus! Are you all right?” Sirius stayed in the water, holding onto the rock. He looked as refreshed as Remus felt, so he must have slept too, in one place or another. His hair was in a new style, braided and pinned up high on his head, with tiny shells woven into it.

“I’m fine now.” Remus swung his legs around to dangle in the water so Sirius could see his ankle was mended. “What about the council? Did they already come?”

“They just left.” Sirius grinned. “It went so well! They hardly noticed. Actually, I think they’re getting sick of checking up on me. They only stayed a few minutes.”

“Really? Thank goodness.” Remus sighed with relief. He still couldn’t imagine the reef or this island without Sirius here. “That’s wonderful. I’m so glad.”

Sirius was still grinning up at him like all of his dreams had just come true. His skin seemed to glow in the afternoon sun, and the shells shimmered with small patches of iridescence.

Remus reached up to run a gentle finger over one of the shells, lingering a bit on Sirius’ hair. “This is different.”

Sirius’ pupils dilated, just a little, and he tilted his head, as if to try to push into Remus’ hand. His voice, however, was casual, betrayed only by the slightest hint of breathlessness. “I-I did it this morning. I was trying to give them the impression that I was _so_ confident and prepared that I had time to do my hair, you know?”

“It’s beautiful.” Remus let his hand trail down the back of Sirius’ head to touch his neck. He felt the small muscles there tremble a little. Sirius rose out of the water an inch or two, as if pulled upwards by his touch, and Remus smiled. “Thank you. For helping me this morning.”

“I’m sorry I didn’t stay,” Sirius said quickly, his eyes fixed on Remus’ face. “I wanted to, but I knew they were coming…”

Remus nodded. “Did you sleep in my bed?”

Sirius looked down, licking his lips nervously. “Yes…is that all right? I wasn’t sure, but I didn’t know how long the song would last, and honestly I was so tired—“

“It’s very all right,” Remus said firmly, interrupting Sirius’ apologies. “You can sleep there whenever you want, whenever you're willing to endure the trial of bipedalism.”

Sirius smiled again, this time in a slow, blooming way when he looked up and saw the same expression on Remus’ face. He rose out of the water a little more, and his hands twitched on the rock, as if he wanted to return Remus' caressing gesture but wasn’t yet sure if he could. Remus felt goosebumps on his neck and shoulder. He could already feel the touch of Sirius’ hand there, like a memory of something that hadn’t happened yet.

“I saw your art,” Sirius said, his voice fluttering a little. “It’s beautiful. I love the one of me and Hari. And all the ones of the reef, too.”

Remus found himself thinking again about all the things he had painted, remembered all the pieces of himself he had allowed to spill out onto paper whenever he drew Sirius. Sirius had seen them all, imperfect as they were. Even now, Remus found himself studying the curve of Sirius’ eyebrows, the angle of his nose, thinking about how he could improve on what he had made.

His gaze dropped downwards an inch, to Sirius’ mouth. That, at least, looked exactly the same as in the paintings. Apparently he had been studying Sirius’ mouth closely for a while now. As he watched, Sirius’ lips parted, and his head leaned back into Remus’ hand as he tilted his chin up in invitation, neck arching with yearning. His eyes were fully dilated now, lids fluttering in a way that matched the shaky breaths Remus was now close enough to feel.

There was a feeling in the center of Remus' chest, something like the pull of gravity. It was gentle, but undeniable, and he was grateful that there was nothing in him that wanted to deny it any longer. He let himself settle into the warm, enveloping sensation like he was sinking his feet into sun-warmed sand and leaned down the rest of the way, turning proximity into touch, turning shared gaze into a kiss.

Sirius sighed in delight, his arms coming up to wrap around Remus’ neck. At the same time, his whole body sank back and down into the water in exactly the same manner as someone swooning, weak-kneed, into bed. Remus went with him, letting himself be pulled along like a patch of seafoam in the tide. They sank together into the cool embrace of the lagoon, the sounds of the waves above replaced by the noise of the sand churning below. It all felt so natural that Remus might almost have thought they had done this already, over months of intimate touches, words whispered against skin.

Sirius seemed to melt into him, his arms warm around Remus' shoulders, his lips pulling gently at Remus' own, his whole body soft and welcoming. There was saltwater in Remus' mouth, which would have been an odd accompaniment to kissing anyone else, but with Sirius it wasn’t odd at all. It was perfect.

Unfortunately, no moment like this, no matter how perfect, could last forever when one participant had a limited air supply. Remus hadn’t cast his swimming charms before he and Sirius had poured themselves into the sea. After only a short minute or so, he had to pull away to literally come up for air.

At the first gentle push, Sirius jerked backwards in surprise and grabbed Remus by the arms, thrusting him bodily up to the surface with a single, powerful undulation. He didn’t stop there either, and pushed Remus up out of the water and onto the sunning stone a second later.

“You don't have your charms on!” he gasped, clearly just realizing this. “Are you all right? Are you drowning?”

He hurriedly pulled himself onto the stone as well, clearly moments away from performing the other kind of mouth-to-mouth.

“I'm fine,” Remus said, trying not to laugh. “I can hold my breath a _little_.”

“Oh!” Sirius looked deeply relieved, and his hand found Remus'. “That's good.”

Even once reassured, Remus was smugly pleased to see Sirius was still breathless, still leaning into him as if Remus was his magnet. Remus leaned in as well, smiling, snaking one arm around Sirius' shoulder.

“Fuck,” Sirius whispered, looking at him as if he couldn’t quite believe his good fortune. “Can I kiss you again?”

Remus remembered what he had said yesterday, _I should have asked_. Now, here he was, asking. It was so sweet and so kind that it made Remus want to kiss every inch of him, not that this was much of a difference in sentiment from a moment ago. As it was, he ended up nodding even as he was bringing their lips back together.

Sirius groaned softly against him, and the kiss gradually took on more intent as Remus pulled himself close against Sirius’ chest, the water on their skin creating patches of coolness that soon warmed from their shared heat. He let his hands wander, stroking down Sirius’ tattooed arms, over his back. After a moment, Sirius did the same, and Remus shivered at the gentle touch of Sirius’ fingers skating over his ribs.

Little by little, Sirius leaned back, letting Remus push him down. The sunning stone was warm against Remus’ arms and knees as he knelt straddling the powerful tail, his hips and chest snug against Sirius’ body. Sirius’ arms were tight around him, his mouth eager but still patient, still gentle.

“So,” Sirius took a breath, looking up at him with his arms looped around Remus’ neck. “Does this mean you’re sexually attracted to me?”

Remus raised his eyebrows. Considering that his erection was now pressed firmly against Sirius’ lower stomach, it seemed unlikely that there could be any doubt about this. Then he saw the vulnerable look in Sirius’ eyes and suddenly understood that this wasn’t really what he was asking. It wasn’t what he had been asking the other day either. Remus smiled softly and answered the more important, underlying question, instead of the one that Sirius had timidly let bob to the surface.

“I’m in love with you.”

“Really?” Sirius raised himself up on his elbows, earnest and utterly adorable in his surprise. 

“Yes.”

Sirius smiled wide, his eyes sparkling with delight, and his smile was so strong it kept returning every few moments as Remus kissed him again.

They settled back into each other, Sirius growing a little bolder now. His hands swept lower down Remus’ back, fingertips tucking themselves gingerly under the waistband of his swim trunks. Remus moaned, pushing his hips so Sirius’ hands slid down even further.

“Fuck, fuck.” Sirius’ voice was hazy and lovely, like the light in the tide pools at dusk. “ _Please_ take these off.”

Remus grinned and lifted himself up just long enough to peel himself out of the wet trunks, laughing at Sirius’ expression, which was honestly more relief than pure lust.

“Fucking finally,” Sirius muttered, pulling him back down into full contact. “I hope you know I want to steal every piece of clothing you own, tie it to a rock, and drop it into the deepest part of the ocean. I _fantasize_ about it.”

“So that's what you’ve been thinking about while you chase your own tail,” Remus teased.

“Well, not only that.” Sirius grinned smugly, wrapping his hands around Remus’ arse with a deliberate grip, pulling his hips down.

Remus moaned at the feeling of Sirius’ warm stomach and the smooth, interspersed scales against the head of his cock. Thanks to all the times Sirius had wrapped his tail around him recently, he already knew how soft the scales on the underside were, unlike the thicker, more protective ones on the dorsal side, but he hadn’t quite been able to conceptualize what an unusual, exquisite sensation they would make when sliding against his cock and inner thighs like this.

Wanting more, Remus pushed himself down lower on Sirius’ body, arms already shaking from holding himself up, and rolled his hips. He kept his movements slow, savoring the decadent reality of touching Sirius at last, and lowered his mouth to Sirius’ chest. He kissed the tattooed star over his sternum, then sought out the other points of the constellation, lingering on Sirius’ nipples, listening to his gasping breaths. He could feel the muscles in Sirius’ tail gradually tensing, could feel the heartbeat under his lips getting faster. He felt much the same, and not just from the self-indulgent slide of his body against Sirius'. It had been quite a while since he had had sex, and he had missed the demonstrative power of it, of being able to affect someone so much.

More evidence of Sirius' arousal made itself apparent a moment later. Sirius' tail curled up between Remus' legs as his back arched, his wide fluke lifting out of the water to drape across Remus' back. The wet, gossamer-thin frill of it on Remus' shoulders was cooler than the rest of Sirius' body, a pleasant contrast to the hot afternoon, like the water of the lagoon itself.

Sirius must have heard him inhale sharply at the sensation, because he took a breath himself before saying, “So, should I put my legs on now?”

“Do you want to?” Remus glanced up at him, but didn’t stop himself from following the elegant line of Sirius' collarbone with his lips.

“What I _want_ is to have sex with you so, literally whatever that means, I want that.” He paused, breathing fast, tilting his neck so Remus could reach his ear. “Fuck. However you're comfortable—it doesn’t matter to me.”

“Yes, it does.” Remus raised himself up on his elbows, giving himself a clear view of Sirius' face, and smiled gently at him. “It matters to you.”

“Remus, if I would do it for _fruit_ , I would do it for you, and gladly.” Sirius leaned up and kissed him with obvious sincerity, but Remus knew better.

“But you'd rather not.”

Sirius lowered his head back to the rock, searching Remus' expression for a moment before reluctantly admitting, “I'd rather not.”

“Then don't. Be yourself.” Remus had never asked a partner to change their body to suit his preferences before, and he wasn’t about to start now. Besides, if matching preferences was Sirius' goal, he would be better off staying the way he was. _This_ was the body Remus had been watching and waiting to cherish for weeks, not the small, unbalanced creature Sirius became when he had legs. Remus turned his head, letting the soft, silver fringe of Sirius' fluke trail across his cheek, and ran his fingers over the thicker cartilage at the edge that controlled the expressive movements. This little experiment proved to be immediately successful, judging by the way Sirius arched his back and tucked his tail around Remus even more tightly.

“Fuck,” Sirius gasped. “Yeah, all right.”

“You’ll have to show me what to do, though,” Remus told him.

Sirius nodded. His hands found Remus’ face and slid into his hair, pulling him close enough for a gentle, lingering kiss. Slowly, he unpeeled his fluke from Remus’ skin, bringing his tail to rest down next to them instead, near their heads. Remus broke the kiss to turn and look.

Sirius’ tail looked much the same as usual, except for the interesting little area near the base of the fluke that Sirius had flirtatiously shown off to him weeks ago—where the scales overlapped each other differently—which was a little swollen. Remus reached out and let his fingers trail over him there, and Sirius sucked in his breath in a shuddering hiss. His fluke was curling in a version of fin-body-language Remus hadn’t yet seen, still fully stretched, but with the edges curving inward, as if looking for something to hold onto.

“Here,” Sirius whispered, his voice shaky. He reached for Remus’ hand, guiding him until Remus’ fingers were enveloped in Sirius’ body and there was a firm shaft pressing against his palm. A moment later, he could see it, as what was inside became outside in one of the evolutionary feats that Sirius liked to use to claim superiority over humans. As usual, Remus couldn’t really blame him. Everything about the Mer, from their language to their body form, was perfectly suited to life in the sea, and having genitals that dangled outside one's body constantly had never seemed very practical to Remus, even on land.

There was something to be said for the aesthetics of the Mer arrangement as well. Sirius’ cock was the same dark, midnight black as the scales on the back of his tail, and it looked stark and almost imposing against the backdrop of silver scales on the underside. It was also wet with a slippery-looking fluid, but Remus hardly registered this, as he was used to Sirius’ entire body being wet more often than not, and it only made sense, considering the depths from which it had just emerged. Aside from those qualities, however, it was shockingly normal in terms of shape and proportion, perhaps just a little wider along the shaft and smaller at the head than the typical human version.

He was aware that Sirius was watching him with an air of calm carefully plastered over what had to be an inner core of nervousness in this vulnerable moment. Under the circumstances, Remus decided to go with a full, ringing endorsement. He leaned over to the side and carefully placed his lips over the tip.

Sirius gasped and convulsed, his hand dropping weakly from Remus’. “ _Fuck_ , Remus!”

Remus hummed back, trailing his tongue over the tip while he held the shaft in a gentle grip. He had expected salt, and that taste was there, but there was also another, more elusive flavor. It was strange, but not unpleasant. Sirius’ cock seemed firmer in his mouth and hand than a human’s would, but that didn’t throw him off either. 

Sirius’ hand found his again, guiding him back down to the base. He swallowed, fingers shaking. “You-you can also…”

Remus followed his lead, letting his fingers sink back into the warm press of Sirius’ body. Sirius’ noises escalated sharply as Remus made a few gentle, experimental thrusts. It only took a minute or two of this to confirm what Remus had already suspected would be the case: morphology just didn’t matter, not when he could so easily reduce Sirius to a breathless, shaking, moaning mess. Besides, he had never minded learning new things. It was part of what made sex interesting and satisfying.

Sirius’ hands were on his back now, holding on and gripping him with increasing tension as he writhed. After a few minutes, he slid one hand up to Remus’ hair, pulling just gently enough to induce Remus to stop. He raised his head, looking over at Sirius’ flushed face and deeply rattled expression.

“Should I be doing something differently?” he asked, hoping Sirius would be honest with him instead of self-conscious, or this learning process would dramatically increase in difficulty.

“No, it’s the other way around,” Sirius reassured him with a breathless laugh, pulling until Remus was lying atop him once more. He cupped Remus’ face and kissed him again, lips soft and shaky in a way that made Remus’ breath catch.

“I just—don’t want to come yet,” Sirius said between desperate, passionate kisses, his hands sliding back down Remus’ back to his hips, pressing their bodies together. “I haven’t even touched you. Fuck, I want to touch you…want to fuck you.”

He stopped himself, eyes widening as if realizing what he had just said, and quickly added, “We don't have to though, if it’s too much—“

“It’s not too much,” Remus said at once. Actually, he couldn’t think of a better outlet for the feelings surging around inside him, or a clearer way to show Sirius how accepting of all this he really was. But there was one problem. “I left my wand up at the house, though. I’m sorry. I was so excited to see you…”

Sirius frowned. “Do you need it?”

“I don’t have a lubricant,” Remus said, hoping this would be enough explanation. Sirius had said he had experience with humans.

Sirius laughed, and Remus felt the vibrations of it in his own chest. Sirius lifted his tail from the sunning stone and brought it back between Remus’ legs, with the lacy fluke resting on his back once more.

“The abyss knows how humans evolved to be a planet-dominating species,” Sirius said, teasing again but with his voice warm in Remus’ ear. He pressed the base of his tail against Remus’ arse, his cock hot and sliding, and Remus moaned suddenly as he felt the warm, dripping wet presence.

“Oh, _oh,_ ” Remus breathed, now understanding that no artificial lubrication would be required. Clearly, Sirius was more than capable of providing.

Sirius kissed him again and then pushed him up into a sitting position with one hand, gaze falling down to Remus’ cock. Remus watched too, as Sirius' palm trailed appreciatively down his chest, then stroked up the inside of his thigh, coating his fingers in the slick fluid there. His hand moved up to Remus’ cock, pulling sweetly. Sirius’ webbed fingers made for a different grip than Remus was used to, but that didn’t stop him from breathing hard and arching his back as the webbing between Sirius’ thumb and forefinger slid over the head of his cock on each stroke. He found himself leaning back, writhing against where Sirius’ cock was pressed against his arse. God, Sirius was almost fucking him already.

“You should—use your fingers first please,” he said, before either of them could get too carried away to be practical. It had been a while, and he knew he would need a few minutes of preparation, both physically and mentally.

Sirius hesitated before saying, “That part you’ll have to do on your own.”

He held up his free hand in demonstration, and Remus realized that, of course, as Sirius’ fingers were webbed, he couldn’t separate them enough for fingering of any depth. It was all or nothing with his hands, and all would rather defeat the point of preparation.

“I can do it,” Remus said quickly. He leaned back down for a better angle, and Sirius welcomed him with a kiss.

There really was more than enough lubrication to go around, and it was reassuringly thick and slippery, as Remus supposed made sense, considering its primary purpose was probably for underwater activities. He had no trouble pushing a finger inside himself, and another shortly after. He couldn’t hold himself up enough to keep kissing Sirius, so he buried his face against his neck instead, biting and sucking just hard enough to leave marks. Sirius continued to stroke his cock the whole while.

The tide was coming in. Remus could feel the cool, welcome water around his knees, and a moment later a larger wave came, sweeping halfway up Sirius' back, as if the lagoon was calling him to return. Sirius shivered at the sensation but didn’t move, except for the occasional twitch of his cock against Remus' arse.

It was so tempting to rush, with Sirius’ cock sliding gently against his knuckles—not impatient, but still there—but Remus didn’t let himself. He wanted to feel every moment of this, every stretch, every shiver of Sirius’ skin under his mouth, every stroke of Sirius’ fingers over his cock.

Even so, it didn’t take long before he was pulling his fingers out and guiding Sirius’ cock in. It was apparent, again, that it was firmer than a human’s, but Remus didn’t mind. He loved the unyielding pressure of it, how he had to be the one to shift and make space. Even more, he loved the panting, overcome expression on Sirius’ face as his cock sank fully in.

“Fuck, _oh_ , Remus, you feel so fucking good,” Sirius moaned. He stopped stroking Remus' cock and fixed both hands around Remus’ hips, holding him still as he took deep breaths, obviously trying to steady himself. This, and the way he had reacted to Remus’ mouth a moment ago, made him suspect that Sirius might be more sensitive than the average human, perhaps a pleasant side-effect of having his cock inside his body on a day-to-day basis, protected from irrelevant stimulation.

“Yeah,” Remus agreed breathlessly, mouth close to Sirius' ear. Sirius’ cock felt amazing, even stationary like this, and he loved how much easier it was for their faces to be close while they did this, a feat that required a bit of flexibility with another human.

He was officially over the concept of waiting and getting adjusted, however. Normally he would solve this problem by simply starting to move, but he didn’t have any leverage with this configuration. Sirius' tail would just move with him. He used his voice instead. “Come on. Sirius, _move_.”

Sirius groaned, but his cock slowly withdrew, pushing back in with a cautious pace that made Remus curse. He pressed his lips against Sirius', let him feel his eagerness for it. “Fuck me, god, please—”

The next thrust was more determined, and the pattern of those following was everything Remus could have wished for in both pace and angle. He moaned breathlessly into Sirius' mouth, transfixed by the intense need on Sirius’ face.

Sirius' fluke was curled around his back again. Remus had noticed the new, curving shape a few minutes ago and had speculated that it looked as though the fluke wanted to hold onto something. He was delighted to realize, now, that the something was him. It hardly moved as Sirius fucked him, since the undulations of the rest of his tail were accomplishing that. It was an anchor, holding Remus in place with delicate but undeniable pressure.

Sirius’ fluke had warmed to Remus' body temperature, so it wasn’t the refreshingly cool curtain it had been earlier, but it still felt wonderful, like his whole self was being wrapped in everything Sirius was. With that and Sirius' smooth chest arching devotedly under him, Sirius' hands around his hips, Sirius' lips pushing with increasingly desperate need at his own, Remus felt entirely enveloped. He felt _safe_ , which was not something he had ever felt so thoroughly with any other partner, especially not in the same moment where he was getting the living daylights fucked out of him. This was an environment where he could truly be himself, where the wolf could be as hungry as it needed to be, where Remus himself could want whatever he wanted.

That thought was just as heady as the firm silhouette of Sirius' cock thrusting in and out of him. Sirius seemed to be falling apart as well. Remus hadn’t had a chance to get to know his signals yet, but from the delirious expression on his face, he had to be close to coming. Remus could feel Sirius' pulse in the veins of his tail, too, and the rapid, pounding sensation was echoed in his own body as if it was contagious, which he supposed it was, in a way.

Sirius' back arched, head tilting away for a moment, and he made a few trilling sounds, as if he had momentarily lost the power of verbal speech. The Mer language seemed oddly sharp and hollow outside the embrace of the water, but, as usual, it was utterly indecipherable.

“What did you say?” Remus asked breathlessly, determined to know whatever it was Sirius said when he was breaking apart with pleasure.

“Fuck,” Sirius groaned, and Remus wondered if this was part of the translation or an in situ exclamation. He tilted his head back down, speaking against Remus' lips. “I said—I said, _fuck_ , you're so fucking beautiful, and I want to see you come.”

Remus reeled with surprise. Even when flirting, Sirius had never called him anything but ridiculous, awkward, and poorly evolved before. Remus hadn’t minded, but he had never expected this complete about-face, to discover that Sirius actually found him beautiful. And, apparently, that wasn’t even _all_ , because Sirius was still talking. He must have packed a lot of meaning into those few short sounds.

“I love you.” He was gasping, crumbling a little more with every thrust of his cock into Remus' arse. Remus could relate. “I want-I want—”

He didn’t finish, and instead shifted abruptly down the rock, sliding with the rhythm of the next wave until his mouth was directly under Remus' cock. His tail stilled for a moment, holding Remus in place as he moved, but he didn’t withdraw. There was no need, Remus realized. If Sirius could reach his own cock with his mouth, he could do this.

“Fuck, fuck,” Remus groaned, lowering his forehead down against the stone so he could have the powerful sight of Sirius' lips, parting and closing over the head of his cock. The feeling of it was even more overwhelming. The waves had been splashing up over Sirius’ stomach, cooling them both, so Sirius’ lips and tongue seemed shockingly warm in contrast. Those same waves were lapping up over Sirius’ cheeks and nose now, but, unsurprisingly, he didn’t seem fazed by this in the slightest. Remus supported himself on one elbow so he could touch Sirius’ face with the other, the tips of his fingers dipping into the water as he brushed Sirius’ cheek. The waves were pulling at the loose strands of his elaborate hairstyle, dampening the shells and restoring their luster.

He felt, more than heard, Sirius moan, and then he began moving his tail again, thrusting his cock at an even faster, more insistent pace than before. Remus cried out, already so close he could feel the foreshadowing of the coming explosion moving throughout his body like a ghost. Then he felt Sirius jerking and moaning beneath him, and looked down to see Sirius’ eyes fluttering with ecstasy as he swallowed around Remus’ cock.

Sirius was fucking him hard at the same time, and Remus gasped and cried out, seeing the evidence of Sirius’ orgasm in his expression, feeling it in the clench of his hands, in the spasming of his fluke, in the pulse of his cock. He felt it in himself as well, as it branched from Sirius directly into him, and he completed the cycle as his orgasm pulsed into Sirius’ mouth.

Images flashed through his mind: fireworks, the lighting-fast pulse of neural networks, the branching complexity of the coral. His thoughts were decadently detailed and yet unformed, tendrils swaying reverently in the tide that swept over them. The rest of him clung to the secure press of Sirius’ body, to the love that saturated his every cell.

For an unknowable period of time afterwards he was nothing but the thrum of his overactive heartbeat in his throat, still beating in time with the pulse he could feel thudding through Sirius’ fluke. Finally, he felt Sirius’ cock easing out of him. Sirius rearranged himself, bringing their faces back level with each other and finding Remus’ lips with his own. His tail relaxed, the wide fluke unpeeling from Remus’ skin and returning to the water below with a splash.

They kissed, dreamy and sated, as the gentle waves continued to roll over the sunning stone, until finally Remus had to sit up or risk being submerged. Sirius smiled up at him, half-floating in the surge, his face full of bliss. Then he stretched, arms yearning up above his head. On the way back down, they wrapped around Remus’ shoulders. His tail undulated, and suddenly they were both in the deeper water in front of the stone. Remus laughed and wrapped his arms around Sirius’ neck, letting himself be supported.

Sirius’ tail swept through the water around them, creating a current, and Remus felt the slippery residue coming away from his legs. It really had gotten everywhere.

“Do I dare make a joke about lagoon pollution?” Remus asked with a wry smile.

“Don’t worry. That’s why I made sure you came in my mouth,” Sirius said serenely. He wrapped his tail around Remus’ legs, finning up, as the Mer called it.

Remus was fairly certain this had to be a joke, despite the complete lack of a tell in Sirius’ expression. He asked, just to be sure. “You’re joking, right?”

“Yes, love.” Sirius grinned and tugged him closer, kissing his cheek, his jaw, the curve of his ear. “Congratulations, you are officially part of the local ecosystem.”

It seemed like he might say more, but suddenly he pulled back, turning to look out at the lagoon, frowning.

“What is it?” Remus asked.

“James is here.”

Remus heard it then too, a low, soothing merfolk song, a bit distorted from their current perspective above the water. Quickly, Remus disentangled himself from Sirius, retrieved his swim trunks from the rocks, and put them on. Sirius was eyeing the trunks with disfavor when James arrived, surfacing next to Sirius.

“So,” he said, as if continuing a conversation from underwater, although Remus hadn’t heard any zipping trills this time, “how did the inspection go? Was this comfort sex or celebratory sex?”

Sirius smiled broadly, tugging Remus back over and kissing his neck with obvious delight. “Celebratory, definitely.”

James cheered and did a quick somersault in the water, splashing them both. “Thank the abyss! I can call off our pod’s blockade maneuvers for the time being, then.”

Sirius laughed and tugged Remus over to James, letting them all fin up together. “Guess what’s even better, Prongs? Remus is in _love_ with me.”

Remus couldn’t hide a smile at Sirius’ utterly infatuated tone. He let his hand trail over Sirius’ lower back under the water, and Sirius tipped his head dreamily onto Remus’ shoulder.

“Really? That’s so wonderful!” James was no less gushy. He said to Remus, “You know, for all his chasing legs, I’ve never seen him as smitten as he was the other day, and you should also know he’s never been in love before this at _all._ ”

“Prongs!!” Sirius’ head jerked up off Remus’ shoulder, and he splashed James in the face with the hand that wasn’t wrapped around Remus’ neck.

“You deserve it,” James said smugly. “Remus, you wouldn’t believe how he teased me for tailing after Lily. You two are an _adorable_ couple, by the way.”

“We really are.” Sirius was already smiling again, although his cheeks were still slightly pink. 

James grinned back, and reached out to put one hand on each of their shoulders. “So, how was it?”

Sirius sighed voluptuously. “Oh, it was _so_ nice, Prongs. He was so sweet and you wouldn’t believe what he can do with his t—“

Cheeks burning, Remus quickly cut him off, “We humans have a rule of etiquette. Don’t kiss and tell.”

Shocked silence fell, and both Sirius and James stared at him like he had just admitted he crushed sand dollars for fun. Then James burst out, “That’s a terrible rule! How do you ever figure anything out?”

He seemed honestly confused. Sirius, on the other hand, seemed less surprised, but he looked so sad and drooping that Remus relented.

“Well, at least don’t kiss and tell in English,” he said with a sigh.

Instantly, Sirius’ beamed, and all of his body language brightened and lifted along with it, from the crown of his head to the tip of his tail. He lunged forward and kissed Remus soundly, then he and James plunged under the water for an intense, trilling conversation. Remus kept his head up with one hand on the sunning stone and pretended he didn’t know what the various gestures signified.

After a minute or two, they resurfaced, both grinning, and Sirius pulled Remus back into his arms. He kissed him behind the ear and then turned to address James. “Were you singing to my sharks earlier?”

“Oh, sorry!” James turned to eye the farther edges of the lagoon. “I didn’t think you would mind, just this once. I wanted them nice and sleepy so they wouldn’t notice the smell of the milk. It’s almost as bad as blood,” he added to Remus.

“Milk?” Sirius jerked in Remus’ arms and then dipped his head under the water, scanning the lagoon.

Remus still didn’t understand what was going on until, moments later, a brown and red blur came shooting across the lagoon, barreling right into their midst in a small explosion of merbaby joy. Lily surfaced a moment later, looking a bit harried but happy.

“Hari!” Sirius laughed with delight. “But—“

“They’re almost a year old now,” James said, ruffling his child’s damp mane of hair. “Close enough, anyways, to come see Uncle Sirius after a life-changing ministry inspection.”

Hari tumbled about in their midst, babbling unintelligibly and climbing on Sirius’ shoulders, trying both to dunk him under the surface and to pluck the seashells out of his hair.

“Hari, leave him be,” Lily said gently. “It looks lovely, Sirius. Is that the five-strand braid I showed you?”

“Yes, and a few ropes,” Sirius said in the moments where his head was still above water.

“I’m going to go get my wand so I can swim properly.” Remus untangled himself after a moment, once it was apparent that the occasion wasn’t about to get any less rowdy any time soon.

“I’ll come with you.” Sirius plopped Hari into James’ arms and followed him onto the shore. “Be right back, guppy!”

Remus grinned at the sudden reappearance of Sirius’ legs. “I do know the way, you know.”

“I’m still getting to know this island,” Sirius said lightly as they started to walk. Hari was watching them forlornly from the shallows. “Who knows what dangers lie in store in this unknowable land-place. There could be chickens.”

Remus laughed. “Chickens are not dangerous, and if they were, you would be no match for one like this.” He nudged Sirius gently with his elbow, his point proven by how Sirius gasped and had to flail his arms to keep his balance, like a man on stilts. “ _I_ think you’re just—how did James put it?— _chasing legs_ again. Apparently it’s a habit! I never would have guessed, seeing as you've spent the whole month calling my legs ridiculous and awkward.”

“Something can be ridiculous for swimming and attractive at the same time,” Sirius said with dignity. “Everyone has a type. You just happen to be mine. Unfortunately, I don’t think you can claim the same about me.”

“Don’t be so sure,” Remus said wryly.

Sirius beamed and grabbed his hand, pulling it up to his mouth for a quick kiss. They held hands for most of the way up to the house, which served both to warm Remus’ heart and correct Sirius’ still-clumsy balance. The walk took longer than it would have if Remus had been on his own, but he didn’t mind.

Once inside, Remus rummaged in the bedding for his wand, and Sirius occupied himself by eating one of the apricots he had left out earlier.

“Oh, so _that’s_ why you came up here,” Remus said as he found his wand under the pillow and strapped it on. “I should have known it was the fruit again.”

“That and…” Sirius swallowed his mouthful and reeled Remus in for a kiss, which turned into more of an involved experience than Remus would have expected, considering the people waiting for them. Remus ended up pressed against his desk, Sirius leaning heavily on him, their bodies fitting together in a way that was completely different than it had been this afternoon, but not at all unpleasant. After several breathless minutes, Remus pulled away, nodding down at Sirius’ temporary new equipment, which was showing significant appreciation for their embrace.

“If _that_ is your goal, we should probably say goodbye to James and everyone first, don’t you think?”

“Yeah.” Sirius swallowed, looking like his feet weren’t solidly on the ground for more than one reason now. He rallied quickly, however. “But, after, we are definitely having legs-sex. It will be so _exotic_.”

Remus made a mock-disappointed noise. “And here I was looking forward to underwater sex.”

Sirius laughed, his arms tightening around Remus’ waist, his head resting on Remus’ bare shoulder. “I love you _so_ much.”

There were still people waiting for them, but Sirius didn’t let go, and Remus didn’t really want to either. After a moment, however, he felt a shift in Sirius’ attention. Sirius’ arm left his waist, and Remus looked over his shoulder to see Sirius was running his hand over one of his paintings, the one with the sharks. Sirius traced the shape of the two of them, Remus curled up small in front of the long lines of Sirius’ body, both of their hands over Remus’ ears.

Sirius’ cheek was still on Remus’ shoulder, so Remus couldn’t see his expression, but his sigh said more than his face could have, the sound heavy with both regret and reverence. “This is your best one, you know.”

As if sensing Remus’ surprise at this, he pulled his face off Remus’ shoulder. “I don’t exactly _like_ it, but…I saw it this morning, and I thought, fuck, he’s taken the most horrible thing I’ve ever done and made it into something I actually want to look at. Even if I don’t like what I feel when I do.”

“You should,” Remus said gently. “I told you, you saved me. That wasn’t a horrible thing to do, even if the consequences were.”

Sirius took a deep breath, looking down at the art again. “That’s what makes it your best. When I look at it, I can almost see it the way you do.”

“I won’t let it happen again, I promise,” Remus said fervently. He had already promised himself that so many times over the last few days, he only just now realized he hadn’t said it to Sirius yet. “And I‘ll help, too, if you think I can. I want to.”

“I know.” Sirius found his hands and held them in his own, his eyes soft, open, and full of love.

They kissed again, slow and decadent enough to make Remus sigh. They were both dripping seawater onto the floor, but Remus was officially done caring. As far as he was concerned, the salt and sand could creep into every corner of his house and life from now on. Eventually, Sirius pulled away.

“Here's how you can help.” He reached around Remus' shoulder and carefully scooped up the drawings. “Waterproof these. I want to show them off to James and Lily.”

Remus had to squash down his protests that they weren’t all done yet, but he did as Sirius asked, and then let himself be pulled out of the one-room house, into the sun.

“Come on,” Sirius was saying. “You can also help give the guppy a tour of our reef.”

“‘ _Our_ reef’?” Remus repeated, eyes wide, heart pounding just as hard as it had last night when Sirius had said he was in love.

Sirius just smiled and wrapped his hand more tightly around Remus’ own. His legs may have been wobbly, but his grip was sure. It said, _I trust you._

Remus squeezed back.

It was a heavy responsibility, to be sure, but Remus couldn’t think of anything that he wanted more. Love and gratitude swelled in his heart, filling him up. He carried that fullness with all the care he had as he and Sirius made their way down the path, each guiding the other in some way as they returned to the reef and to the excited little family splashing in the waves. 

THE END


	6. Bonus Coloring Pages

**Notes for the Chapter:**

> For all you lovely people I have TWO coloring pages of pretty pretty Sirius. These are the result of a collaboration between me and my wife, the most beatiful, clever, and talented mermaid in all the seven seas. She drew the unfairly beautiful Siriuses, and I drew the coral & fishies, and I did all the inking and the photoshop work. 
> 
> Note, I somehow neglected to ink Sirius' tattoos in the first one??? I will fix it eventually. Or you can draw your own! I might also update the second one with a rock for Sirius to sit on...maybe even a dramatic splashy wave in the background...
> 
> I'm working on coloring my own versions of these. I will post them here and on tumblr once they are done. :)

In His Element:

[ ](https://www.flickr.com/photos/158228914@N03/50756378473/in/dateposted-public/)

_“Stop being a bottom feeder and let me show you my reef already.”_

[Find a high resolution version to print and color here!](https://drive.google.com/file/d/1oNlaMy-wz8QZEqKp-yG1zBiQoWDwdiFc/view?usp=sharing)

* * *

"Curious, Little Primate?"

[ ](https://www.flickr.com/photos/158228914@N03/50757116171/in/dateposted-public/)

_"There’s a reason they call it getting tail.”_

[Find a high resolution version to print and color here!](https://drive.google.com/file/d/1RDl-bZnPBWOF_no0Hrf3ybx8OYfMaVgm/view?usp=sharing)

**Notes for the Chapter:**

> I would L O V E to see pictures of anything you color! 
> 
> [Send them to me on tumblr ](xinasvoice.tumblr.com)and I promise to be inappropriately excited <3

**Author's Note:**

> Comments are good karma!  
> …unless you are a marine biologist here to lecture me about electroreception and types of barnacles, in which case I may have to throw you in the lagoon.
> 
> I'm thinking I will write more in this universe at some point, so I made a series so you can subscribe to it. But, be warned, I write very slowly! [Hit me up on tumblr ](xinasvoice.tumblr.com), in the meantime, eyyy <3


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